Wyniki wyszukiwania - BazTech

1

Hydrodynamics and turbulence anisotropy for complex flow in a sinuous channel

Taye Jyotismita, Kumar Bimlesh

Acta Geophysica

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2022

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Vol. 70, no 5

2269--2282

EN

Sinuous channel flows are the most natural form of alluvial streams. The complex flow in the channel bends has been the main focus of the study. This paper examines the flow velocity and the three-dimensional velocity fluctuations in a pure sinuous channel. The main focus of the study is on the characterization of turbulence anisotropy along the sinuous bend. Experiments were conducted in a sinuous channel of a rectangular cross-section to identify the turbulence present in the flow. Secondary flow, Reynolds shear stress, turbulent kinetic energy, and anisotropy turbulence were evaluated in the sinuous bend. The bend apex is composed of a large circulation cell at the center of the bend section. The maximum Reynolds shear stress (RSS) is located at the bend apex with the streamwise-transverse and transverse-vertical components of RSS showing high peaks of positive and negative values. This fact is in support of the secondary flow observed in this study. Anisotropic stress tensors were estimated at different bend sections and are shown to have greater contribution toward streamwise and transverse direction. Anisotropic invariant map (AIM) identified the turbulence at bend sections and varying flow depth. Two dimensional, cigar-shaped, and pancake-shaped turbulence was observed at the bend upstream and downstream. Isotropic turbulence was observed at the bend apex. Near the bed (z∕h ≤ 0.2) and away from the bed (z∕h ≥ 0.4), pancake-shaped and cigar-shaped turbulence was observed.

2

Enhancement of Aerodynamic Efficiency of Aerofoil Using Improved Blowing and Suction System

Balaji K., Wessley G. Jims John

Advances in Science and Technology. Research Journal

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2021

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Vol. 15, no 2

116--126

EN

Improved Blowing and Suction System (IBSS) is a novel concept that can be effectively implemented in future aircraft to improve the aerodynamic performance of aircraft wings. The proposed IBSS consists of a regular wing without its secondary control surfaces and with a Pump. The injection and suction system is used to create additional flow without disturbing the main flow over the aerofoil which effectively delays the boundary layer separation. The injection and suction areas are kept constant and they are located just below the maximum thickness point and suction is created close to the trailing edge. This paper presents a detailed numerical analysis of the proposed IBSS and the study shows that the stalling angle of attack is increased by 60% while the coefficient of lift is increased 37.5% compared to the baseline aerofoil. Also, the commercially used coflow jet (CFJ) method stalls at a 12° angle of attack whereas with the proposed IBSS method the stall occurs at a 16° angle of attack. The stalling angle is thus delayed by 33%, thus increasing the aerodynamic performance of the wing as compared to the existing methods. Also, any malfunction in IBSS does not significantly affect the performance of the aircraft. The implementation of IBSS will lead to a reduction in the weight of the aircraft and the elimination of secondary control surfaces.

3

Numerical investigation on the transition of fluid flow characteristics through a rotating curved duct

Hasan Mohammad Sanjeed, Islam MD. Sirajul, Badsha MD. Faisal, Mondal Rabindra Nath, Lorenzini Giulio

International Journal of Applied Mechanics and Engineering

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2020

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Vol. 25, no. 3

45--63

EN

Time-dependent flow investigation through rotating curved ducts is utilized immensely in rotating machinery and metal industry. In the ongoing exploration, time-dependent solutions with flow transition through a rotating curved square duct of curvature ratio 0.009 have been performed. Numerical calculations are carried out for constant pressure gradient force, the Dean number Dn = 1000 and the Grashof number Gr = 100 over a wide range of the Taylor number values […] for both positive and negative rotation of the duct. The software Code:Blocks has been employed as the second programming tool to obtain numerical solutions. First, time evolution calculations of the unsteady solutions have been performed for positive rotation. To clearly understand the characteristics of regular and irregular oscillations, phase spaces of the time evolution results have been enumerated. Then the calculations have been further attempted for negative rotation and it is found that the unsteady flow shows different flow instabilities if Tr is increased or decreased in the positive or in the negative direction. Two types of flow velocities such as axial flow and secondary flow and temperature profiles have been exposed, and it is found that there appear two- to four-vortex asymmetric solutions for the oscillating flows for both positive and negative rotation whereas only two-vortex for the steady-state solution for positive rotation but four-vortex for negative rotation. From the axial flow pattern, it is observed that two high-velocity regions have been created for the oscillating flows. As a consequence of the change of flow velocity with respect to time, the fluid flow is mixed up in a great deal which enhances heat transfer in the fluid.

4

Prediction of secondary flow losses in an entrance duct to a low-pressure turbine

Jonak P., Borzęcki T., Kubacki S.

Archives of Mechanics

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2019

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Vol. 71, nr 1

65--90

EN

Secondary flow features and total pressure losses by means of the total pressure loss coefficient are discussed in an entrance duct, named a turbine central frame (TCF), to a four-stage low-pressure turbine (LPT) of aero-engine. The massaveraged total pressure losses are also analysed at outlets from selected components of the low-pressure turbine. The Reynolds-averaged Navier–Stokes (RANS) technique has been employed for prediction of mean flow characteristics. The numerical results are compared with experimental data obtained in Polonia Aero Lab in Zielonka (Poland). Good agreement is obtained between measured and predicted global flow characteristics and the pressure coefficient on a surface of an inlet guide vane. The high values of the loss coefficient are observed at endwalls, in cores of streamwiseoriented vortex structures near to the endwalls and in the wakes behind the vanes. It is found that the endwall losses contribute by far the most to the total losses at the outlets from the turbine central frame and first vane-row and they become lower at an outlet f rom the first blade-row and at outlets form consecutive vane- and blade-rows.

5

Pomiar PIV przepływu niestacjonarnego w kadzi wirowej

Jakubowski M.

Pomiary Automatyka Kontrola

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2013

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R. 59, nr 7

632--635

PL

Praca przedstawia problemy pomiarowe jakie powstały podczas zrealizowanego cyklu badań z wykorzystaniem techniki pomiaru bezkontaktowego PIV (Particle Image Veolcimetry) przepływu niestacjonarnego w zbiorniku modelowym kadzi wirowej zwanej potocznie whirlpoolem. Obiektami badań były zbiorniki wykonane z PMMA o zróżnicowanym konstrukcyjnie rozmieszczeniu otworów wlotowych. W pracy zaprezentowano zbudowane stanowisko pomiarowe, sposób kalibracji, problemy i ograniczenia zastosowania PIV powstałe podczas prowadzenia badań oraz przykładowe wyniki analiz.

EN

The paper presents measurement problems which occurred during the series of research incorporating the PIV (Particle Image Velocimetry) optical measurement of unsteady ﬂow inside a scale model of a cycling vat, also known under the name of whirlpool. The subject of the research were containers made of PMMA with structurally diversiﬁed placement of inlets. The work unveils the workbench, the calibration method and the limitations of adopting PIV met during the research, along with sample results of analysis. The measurements were taken on a workbench built in the laboratory of Philadelphia Mixing Solutions, Palmyra PA, US. The measurements incorporated a PIV FlowSense2M camera, a DantecDynamics’ HUB system as well as YAG NewWave Solo 120 TX laser equipped with a controller, a part of which is a water-cooling system. FlowManager was the software used for computation, whereas DynamicStudio was used for analysis and result collection. While obtaining measures an array of difﬁculties was met, related to capturing decent quality images with seeding particles under speciﬁc conditions of ﬁlling up the whirlpool tank. The phenomenon of free surface inside the ﬂow and the characteristics of ﬁlling up an open tank have revealed multiple complications connected to laser beam reﬂections along with capturing reﬂections from other light sources. An addi-tional trouble was caused by aeration of the mixture being the subject of the measurement. Unsteady ﬂow was the cause of problems during analysis of the material, so it was necessary for adaptive correlation to be based on two frames. This is not the case with steady ﬂow, for which we can use 1000 consecutive frames as a basis for the statistic analysis.

6

Non-symmetrical boundary layer suction in a compressor cascade

Liesner K., Meyer R., Schulz S.

Journal of Theoretical and Applied Mechanics

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2012

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Vol. 50 nr 2

455-472

EN

In order to simulate non-symmetrical boundary layer suction in an annular compressor, a cascade investigation has been performed with single-sided suction slots only. A preceding investigation had revealed a high potential for loss reduction by two different types of boundary layer suction. The experimental investigation was performed with five NACA 65-k48 stator blades at the design Mach number of 0.67 and Reynolds number of 560.000. The two investigated suction geometries are a narrow slot following the design of Peacock and a wider slot of own origin, both slots are positioned on one side of the passage only. The Peacock slot is placed in the corner between suction side of the vane and the side wall, the wider slot is positioned from suction side to pressure side following the side wall’s flow detachment line. With half the suction rate of the preceding investigation the efficiency of the cascade could still be enhanced. In the case with 2.5% suction rate the total pressure loss coefficient of the full passage was decreased by 13%, in the case with 1% suction rate the loss coefficient was decreased by even 10%. The outflow of the cascade is as expected no more symmetrical and the one sided suction has no large impact on the flow of the opposite side of the passage.

PL

W pracy przeprowadzono symulację problemu zasysania czynnika w niesymetrycznej warstwie przyściennej sprężarki, analizując kaskadę z jednostronnymi wlotami ssącymi. Badania poprzedzające ujawniły wysoki potencjał w ograniczaniu strat przy zastosowaniu dwóch różnych rozwiązań sposobu zasysania w warstwie przyściennej. Doświadczenia przeprowadzono, używając pięciu łopatek kierownicy sprężarki NACA 65-K48 projektowanej do przepływu przy prędkości 0.67Ma i liczby Reynoldsa 560000. Geometria obydwu rozwiązań zasysania wykorzystuje projekt wąskiej szczeliny wlotowej R.E. Peacocka oraz projekt własny szczeliny szerszej, przy czym obydwa typy umiejscowiono wyłącznie po jednej stronie kanału przelotowego. Szczelinę Peacocka umieszczono w rogu pomiędzy stroną ssącą łopatki oraz ściany, natomiast szczelina szeroka pokrywa obszar od strony ssącej do sprężającej wzdłuż linii odrywania przepływu. Przy tempie zasysania stanowiącym połowę wydatku stosowanego w poprzedzających badaniach nadal odnotowano możliwość zwiększenia sprawności kaskady. Przy spadku tempa ssania do 2.5%, współczynnik całkowitych strat ciśnienia zmalał o 13%, natomiast dla dalszego spadku do 1% współczynnik ten zmniejszył się o 10%. Zgodnie z oczekiwaniami wypływ z kaskady utracił symetrię, a zasysanie jednostronne nie zmieniło znacząco charakteru przepływu na przeciwnej stronie kanału przelotowego.

7

A parameter study on the influence of fillets on the compressor cascade performance

Meyer R., Schulz S., Liesner K., Passrucker H., Wunderer R.

Journal of Theoretical and Applied Mechanics

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2012

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Vol. 50 nr 1

131-145

EN

In order to evaluate the influence of fillets in a high speed compressor cascade with an aspect ratio of h/c = 1 a parameter study has been performed. Fillets of different radii from 1 to 5mm (2.5%c-12.5%c) between the side wall and stator vanes have been investigated at inlet Mach numbers of M = 0.5 and M = 0.66 and at a Reynolds number of Re = 5.6 ź 105 based on the chord length. The heights of the fillets were chosen with regard to manufacturing aspects for blade integrated disks (Blisk). The measurements were accomplished with a total pressure rake combined with angle probes which provides information on total pressure loss, efficiency and outflow angle of the cascade. For comparison and estimation of the performance of the fillet equipped cascade a reference cascade without fillets was measured and the differences between the individual test cases will be shown in quantitative numbers and values as well as qualitative pictures. In the measurements for this paper a dependence between the fillet height and the total pressure loss coefficient became apparent.

PL

W celu oszacowania wpływu powierzchni przejściowej łopatek w wysokoobrotowych sprężarkach kaskadowych o współczynniku kształtu h/c = 1 na ich wydajność w pracy przeprowadzono analizę parametryczną układu. Profile przejściowe o promieniach zaokrągleń od 1 do 5mm (2.5%c-12.5%c) pomiędzy powierzchnią osadzenia a łopatką kierownicy badano dla prędkości napływu 0.50-0.66M i liczbie Reynoldsa Re = 5.6 ź 105 przy zadanej długości cięciwy łopatki. Wysokość profilu przejściowego dobrano ze względów technologicznych typowych dla dysków zintegrowanych z łopatkami. Pomiary dokonano za pomocą czujników ciśnienia i próbników kątowych, co pozwoliło na zgromadzenie informacji o całkowitych stratach ciśnienia, sprawności i wartości kąta odpływu z kaskady. Dla celów porównawczych i wyznaczenia wydajności sprężarki przeprowadzono pomiary w kaskadzie referencyjnej pozbawionej powierzchni przejściowych. Różnice dla poszczególnych testów pokazano ilościowo na wartościach konkretnych parametrów i jakościowo na odpowiednich rysunkach. Pomiary wykazały wyraźną zależność pomiędzy wysokością profilu przejściowego i współczynnikiem całkowitych strat ciśnienia.

8

Symulacja przepływu płynu w kadzi wirowej o wielopunktowym napełnianiu

Sterczyńska M., Jakubowski M.

Inżynieria Rolnicza

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2012

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R. 16, nr 3

227-235

PL

Praca prezentuje porównanie wyników uzyskanych dla modelu symulacyjnego CFD (Coputational Fluid Dynamcs) kadzi wirowej o napełnianiu jednostronnym (klasycznym) i zwielokrotnionym po obwodzie. Przedmiotem analizy było określenie wpływu zastosowania napełniania z wykorzystaniem czerech otworów rozmieszczonych symetrycznie na płaszczyźnie płaszcza zbiornika kadzi wirowej na występowanie przepływ wtórnego odpowiedzialnego za formowanie się stożka osadu gorącego. Analiza czasów formowania oraz wartości prędkości maksymalnej przepływu wtórnego który jest odpowiedzialny za powstawania specyficznego kształtu stożka osadu wykazała zróżnicowanie wyników w zależności od wariantu napełniania. W odniesieniu do klasycznego napełniania korzystniejsze warunki (skrócenie czasu powstawania przepływu formującego stożek osadu oraz wyższą wartość prędkości) uzyskano przy napełnianiu wielostronnym.

EN

The paper presents the comparison of simulation results obtained for the Computational Fluid Dynamics CFD) model of the whirlpool tank of one-sided inflow (classic) and multiplied by the circumference. The subject of the analysis was to determine the effect of using four inlets placed symmetrically on a whirlpool plane of the tank on the occurrence of the secondary flow which is responsible for the formation of the hot trub cone. Analysis of the formation time and the speed of the secondary flow which is responsible for the formation of the specific shape of the cone of sediment results showed differences depending on the variant of the filling. With respect to the classical filling better conditions (shorter cone formation forming sediment flow and higher speed) achieved during the filling multilateral.

9

A bifurcation study of laminar thermal flow through a rotating curved duct with square cross-section

Mondal R. N., Roy S. C., Datta A. K., Uddin M. K.

International Journal of Applied Mechanics and Engineering

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2012

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Vol. 17, no. 4

1193-1211

EN

In this paper, a comprehensive numerical study is presented for the fully developed two-dimensional flow of viscous incompressible fluid through a rotating curved duct with square cross section. Numerical calculations are carried out by using a spectral method and covering a wide range of the Taylor number […] for two cases of the Dean numbers, Case I: and Case II: . A temperature difference is applied across the vertical sidewalls for the Grashof number , where the outer wall is heated and the inner one cooled. The positive rotation of the duct about the center of curvature is imposed, and the effects of rotation (Coriolis force) on the flow characteristics are investigated. As a result, two and three branches of asymmetric steady solutions with two-, three- and four-vortex solutions are obtained by using the Newton-Raphson iteration method. Linear stability of the steady solutions is then investigated. When there is no stable steady solution, time evolution calculations as well as their phase spaces are obtained and it is found that the periodic solution turns into transitional chaos or chaotic solution through multi-periodic oscillation, if is increased. Secondary flow patterns and temperature profiles characterizing the flow are also obtained.

10

Model symulacyjny przepływu w kadzi wirowej o zwielokrotnionym zasilaniu

Jakubowski M.

Postępy Techniki Przetwórstwa Spożywczego

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2011

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nr 2

58-61

PL

Artykuł prezentuje wyniki obliczeń opracowanego modelu symulacyjnego CFD (Computational Fluid Dynamics) dla przepływu płynu w zbiorniku kadzi wirowej typu Whirlpool. Przedmiotem analizy było porównanie przepływu dla dwóch wariantów zasilania kadzi wirowej - jednostronnego (klasycznego) i podwójnego, zwielokrotnionego po obwodzie. Celem analizy było określenie wpływu zastosowania zwielokrotnionego zasilania na stan i charakter przepływów wtórnych występujących podczas wirowania płynu w zbiorniku kadzi wirowej.

EN

The paper presents the results of calculations of the model simulation CFD (Computational Fluid Dynamics) for fluid flow in the whirlpool tank. The analysis was to compare for inflow in the two variants of the whirlpool inlets constructions - single (classical) and a double, multiplied by perimeter. The purpose of the analysis was to determine the effect of the use multiplied inflows to the state and nature of secondary flows that occur during spinning fluid in the whirlpool tank.

11

Unsteady MHD Couette flow through a porous medium in a rotating system

Kumar N., Gupta S.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 4

1037-1049

EN

An unsteady hydromagnetic Couette flow of a viscous incompressible fluid through a porous medium overcrowded between parallel porous non-conducting plates, rotating with a uniform angular velocity about an axis normal to the plates is considered. The flow is generated by the motion of the upper plate. The fluid and plates rotate in unison with the same angular velocity. An exact solution of governing equations is obtained by using the Laplace transform. Solutions for velocity distributions as well as the coefficient of skin-friction are obtained and their profiles for various values of physical parameters are shown through graphs.

12

Investigation of endwall flows and losses in axial turbines. Part II. The effect of geometrical and flow parameters

Lampart P.

Journal of Theoretical and Applied Mechanics

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2009

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Vol. 47 nr 4

829-853

EN

Results of numerical investigations based on a 3D RANS solver FlowER, explaining the effects of geometrical and flow parameters on the development of endwall flows are presented. The blade height-to-chord ratio, flow turning in the cascade, inlet angle and radial distribution of pressure and profile load are considered here. It is also shown how the secondary flow patterns change in the case of non-nominal incidence at the suction side of the blade and due to interaction with shroud leakage and periodical turbine wakes.

PL

W pracy przedstawiono wyniki obliczeń numerycznych wpływu parametrów geometrycznych i przepływowych palisady turbinowej na rozwój przepływów brzegowych. Rozważano wpływ stosunku wysokość/cięciwa łopatki, odchylenia przepływu w palisadzie, kąta wlotowego oraz promieniowego rozkładu ciśnienia i obciążenia profilu. Pokazano także jak zmienia się obraz przepływów wtórnych w przypadku nienominalnego napływu na stronę ssącą łopatki oraz podczas oddziaływania przepływu głównego z przeciekiem nadbandażowym i periodycznymi śladami spływowymi. Obliczenia wykonano z pomocą programu FlowER, solwera modelu 3D RANS.

13

Investigation of endwall flows and losses in axial turbines. Part I. Formation of endwall flows and losses

Lampart P.

Journal of Theoretical and Applied Mechanics

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2009

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Vol. 47 nr 2

321-342

EN

Endwall flows are among the most important sources of loss in turbines. The process of formation of endwall flows and evolution of vorticity from the endwall boundary layers is briefly described in the paper. The resulting endwall losses are discussed. The endwall boundary layer losses are evaluated theoretically by integrating the entropy increase in the boundary layer and assuming a certain model of blade profile load. The endwall losses are also calculated with the help of CFD in a 3D straight turbine cascade of Durham and compared with the results of available experimental data of ERCOFTAC.

PL

Przepływy brzegowe stanowią jedno z głównych źródeł strat w turbinach. W pracy w skrócie wyjaśniono proces formowania się przepływów brzegowych i ewolucję wirowości pochodzącej z brzegowych warstw przyściennych. Przedyskutowano wynikające stąd straty przepływu. Wyznaczono teoretycznie straty przepływu w brzegowej warstwie przyściennej poprzez całkowanie przyrostu entropii wzdłuż warstwy brzegowej i zakładając pewien model obciążenia profilu łopatkowego. Z pomocą programów komputerowych numerycznej mechaniki płynów wyznaczono także przepływ i straty brzegowe w prostej palisadzie turbinowej Durham i porównano otrzymane rezultaty z danymi eksperymentalnymi ERCOFTAC.

14

Ruch płynu w kadzi wirowej whirlpool

Jakubowski M., Diakun J.

Inżynieria Rolnicza

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2009

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R. 13, nr 2

57-65

PL

W pracy przedstawione zostały matematyczne opisy ruchu cieczy w kadzi wirowej wyjaśniające powstawanie przepływu wtórnego odpowiedzialnego za formowanie się stożka osadu. Zaprezentowano pełny model matematyczny ruchu płynu w zbiorniku kadzi wirowej, uproszczone rozwiązanie opisujące powstawanie przepływu dla pojedynczej warstwy w obszarze granicznej warstwy cieczy przy dnie zbiornika oraz model komputerowy ruchu płynu w zbiorniku kadzi wirowej whirlpool.

EN

Paper presents the mathematical descriptions of the liquid flow in the whirl-settling vat that explain formation of the secondary flow responsible for the hot trub cone forming. The full rotating fluid flow in the whirlpool vessel, the simplified solution describing formation of the secondary flow in the boundary layer near the bottom vessel and the computational model of the rotating liquid flow in the whirl-settling vat has been presented.

15

Results of the experimental testing of a stage with 3D shaped blades and design of a new stage

Hoznedl M, Milčák P

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2008

|

nr 133

229--236

EN

The paper shows some results from the experimental testing of a turbine stage equipped with 3D shaped stator blades. Data measured behind the stator and rotor clearly revealed the difference between Compound Lean and Compound Twist blades. The effects of the 3D stator shaping on flows are presented in comparison with classical Prismatic blades. The design of a new stage with 3D shaped stator and also rotor blades is described.

16

Wpływ strat brzegowych w obszarze przepływów wtórnych na kształtowanie wirnika sprężarki promieniowej

Puzyrewski R., Flaszyński P.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

|

2006

|

nr 130, vol. 1

153-162

PL

Przedstawiono metodę wyznaczania powierzchni łopatki sprężarki promieniowej opartą o rozwiązanie zadania odwrotnego w ramach modelu osiowosymetrycznego. Wykorzystano korektę Stodoli dla uwzględnienia skończonej ilości łopatek. Pokazano jak zwiększone straty w obrębie obszarów przy dysku i pokrywie wpływają na zmianę kształtu łopatki. Dla przykładowego wirnika wykonano obliczenia typu 3D.

17

Wpływ zmiany kształtu układu na intensyfikację wnikania ciepła i masy w procesie elektrohydrodynamicznym

Wolny A.

Inżynieria i Aparatura Chemiczna

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2004

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Nr 3s

185-186

EN

It has been shown, that the experimental results obtained in the simple process of evaporation from a flat surface in the electric field can be used in design of the complex EHD process of a ceramic element drying.

18

Laser-Doppler velocimetry - a powerful tool to investigate the flow behavior of polymer melts

Merten A., Schwetz M., Münstedt H.

International Journal of Applied Mechanics and Engineering

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2003

|

Vol. 8, no spec.

283-288

EN

The flow behavior of a low density polyethylene (LDPE) and a high density polyethylene (HDPE) melt in the entrance region, the interior of slit, and within a slit die was investigated by means of laser-Doppler velocimetry (LDV). Large vortices were found upstream of the die with for the LDPE. The HDPE did not exhibit any vortices. The velocities within the vortices are about 100 times smaller than those in the center of the flow. Far-reaching consequences for processing arise as the residence time of the melt in the vortices is long. The velocity distribution along the channel axis reveals large elongational deformations near the contraction. The elongational velocities are much higher than those attainable by elongational rheometers. For the HDPE it could be shown that the material slips at the wall.

19

Flow in a skewed compound open channel with trees on a flood plain

Fukui Y., Urayama T., Takamizu K.

Archives of Hydro-Engineering and Environmental Mechanics

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2003

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Vol. 50, nr 1

3-19

EN

In this research, the flow in a skewed compound channel with trees on the flood plain along the skewed part is studied. Three cases are assumed. Namely, 1) there are no trees on the flood plain along the main skewed part; 2) there are many trees on the flood plain set in order; and 3) there are many trees on the flood plain in disorder. In this research, 1) changes of water level and velocity in the channel; 2) the de-velopment of secondary flow as water flows downward; 3) the drag force due to the existence of trees; and 4) the changes of the river bed level in a movable bed condition are investigated. Numerical analyses using 2-D shallow water theory are also carried out to reproduce a flow in the skewed channel. As a result, the hydraulic quantities, for example water depth and the velocity cal-culated for a case setting trees in order and close together, are available in the river planning for a situation in which some of the trees were washed downstream. Such hydraulic quantities become severe for conditions in order and close to-gether in the flood. During the experiment using sand, channel beds are deformed by piling up and digging of sands or stones in various cases.

20

Numerical simulation of the influence of a fillet and a bulb on the secondary flow in a compressor cascade

Hoeger M., Schmidt-Eisenlohr U., Gomez S., Sauer H., Müller R.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2002

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Vol. 6, No 1

25-37

EN

Large fillet radii are typically found on highly loaded compressor rotors to ensure structural integrity. The objective of this paper is to investigate the impact of such real geometry effects on the flow at the hub section. Investigations were performed numerically for the idealised case of a plane compressor cascade with the 3D Navier-Stokes code TRACE_S. Realistic inlet boundary layer displacement thickness and typical loading levels close to stall are considered at low inlet Mach numbers Ma1 = 0.23. A large fillet with a relative radius of 16% chord length is considered as well as a 3D leading edge bulb-configuration designed at TU Dresden. The results are discussed in terms of iso-Mach surfaces, secondary flow patterns and spanwise incidence and turning. A complex 3D vortex system rises from the fillet radius, which improves the aerodynamic behaviour of the cascade at the end-wall section. With the bulb configuration the suction surface horse-shoe vortex leg was demonstrated to weaken the undesirable cross flow and by that to reduce the hazard of corner stall.