Wyniki wyszukiwania - BazTech

1

Shock wave induced flow separation control by Air-Jet and Rod Vortex Generators

Tejero F., Doerffer P., Szulc O.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2015

|

Vol. 19, No 2

167--180

EN

Flow separation control by Vortex Generators (VGs) has been analyzed over the last decades. The majority of the research concerning this technology has been focused on subsonic flows where its effectiveness for separation reduction has been proven. Less complex configurations should be analyzed as a first step to apply VGs in transonic conditions, commonly present in many aviation applications. Therefore, the numerical investigation was carried out for a Shock Wave-Boundary-Layer Interaction (SWBLI) phenomenon inducing strong flow separation at the suction side of the NACA 0012 profile. For this purpose, two kinds of VGs were analyzed: well documented Air-Jet Vortex Generators (AJVGs) and our own invention of Rod Vortex Generators (RVGs). The results of the numerical simulations based on the RANS approach reveal a large potential of this passive flow control system in delaying stall and limiting separation induced by a strong, normal shock wave terminating a local supersonic area.

2

Parallelized numerical code for derivation of heat transfer coefficient from experimental data

Telega J., Doerffer P., Szwaba R., Kaczyński P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2015

|

Vol. 19, No 2

197--205

EN

An application of parallel computation capabilities in the MATLAB language for the analysis of experimental data concerning the heat transfer coefficient on ribbed walls is presented in this paper. A description of the experimental study, mathematical model and numerical implementation is also given. The obtained results of measurements and calculations shown here clearly indicate the influence of ribbed walls on the heat transfer coefficient distribution in an internal, subsonic flow.

3

Numerical simulations of gap flow above rotating disk

Wasilczuk F., Flaszyński P., Doerffer P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2015

|

Vol. 19, No 2

89--100

EN

A rotating disk can be considered a basic configuration for the investigations of the impact of various conditions on the flow through the clearance between the shrouded turbine blade and the casing. Numerical calculations using Fine/Turbo Numeca were conducted to examine the influence of the rotational velocity and the pressure difference across the disk on the flow conditions, especially the mass flow through the clearance. The results were validated using the experimental data. Moreover, the flow field was investigated to reveal the vortices induced in the flow. The calculations showed a significant drop of the mass flow with a rise of the rotation velocity. Additionally, the vortex created upstream of the disk at higher rotation velocities was observed. The phenomenon of separation at the edge of the disk was investigated.

4

Numerical analysis of high-speed impulsive (HSI) noise of PZL W3-A "Sokół" (Falcon) helicopter main rotor in forward flight

Szulc O., Doerffer P., Tejero F., Żółtak J., Małecki J.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2015

|

Vol. 19, No 2

181--196

EN

The paper presents the results of a numerical simulation of the flow and acoustic field generated by the PZL W3-A “Sokół” (Falcon) helicopter main roto in high-speed forward flight conditions based on the URANS approach and the chimera overlapping grids technique. A refined CFD model (40+ million of control volumes, 600+ blocks chimera mesh) was designed to resolve the flow-field together with the low-frequency content of the acoustic pressure spectrum in the near-field of the rotor blades to allow high-speed impulsive (HSI) noise prediction. Detailed 3D data was recorded for one rotor revolution (approx. 3 TB) allowing exceptional insight into the physical mechanisms initiating the occurrence and development of the HSI noise phenomenon.

5

Influence of membrane amplitude and forcing frequency on synthetic jet velocity

Kurowski M., Doerffer P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2015

|

Vol. 19, No 2

111-120

EN

This paper presents the results of numerical investigations of a synthetic jet actuator for an active flow control system. The Moving-Deforming-Mesh method as a boundary condition is used to capture the real physical phenomenon. This approach allows precise investigation of the influence of the membrane amplitude, the forcing frequency and cavity effect on the jet velocity. A synthetic jet actuator is simulated using a membrane perpendicular to the surface arrangement. Two cases are investigated to maximize the jet velocity – an actuator with one and two membranes in a cavity. Two main forcing frequencies can be specified in the synthetic jet actuator application. One corresponds to the diaphragm natural frequency and the other corresponds to the cavity resonant frequency (the Helmholtz frequency). This study presents the results of actuators operating at the two abovementioned forcing frequencies. The simulation results show an increase in the jet velocity as a result of an increase in the membrane peak-topeak displacement. This study was a preliminary study of the synthetic jet actuator for single and double membrane systems. The optimization process of the synthetic jet actuator geometry and parameters is ongoing. Numerical results obtained in these investigations are to be validated in the experimental campaign.

6

Influence of air cooling and air-jet vortex generator on flow structure in turbine passage

Szwaba R., Flaszyński P., Szumski J. A., Doerffer P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2015

|

Vol. 19, No 2

153--166

EN

The paper concerns the experimental investigations and numerical simulations of a high loaded model of a turbine blade. An increase in the blade load leads to enlargement of a local supersonic zone terminated by a shock wave on the suction side. The Mach number upstream of the shock reaches up to 1.6. The interaction of the shock wave with a boundary layer at such a high Mach number leads to a strong separation. Streamwise vortices generated by air-jets were used for the interaction control. The work presents the experimental and numerical results of the application of an air-jets vortex generator on the suction side of cooled turbine blades. Very interesting results were obtained in the context of the air cooling and air-jet vortex generator influence on the flow structure in the turbine passage.

7

Hole extension effect on transpiration flow efficiency

Lewandowski T., Doerffer P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2015

|

Vol. 19, No 2

121--128

EN

The present analysis of the hole extension effect on the transpiration flow efficiency is a part of the research [1] which aims at defining a physical transpiration model of the flow through perforated plates. Perforated walls find a wide use as a method of flow control and effusive cooling. Some data on the L/D (hole length to diameter ratio) effect on the flow structure and mass flow rate may be found in the literature [2, 3], but all those works concern holes of a diameter at least one order of magnitude larger than those used in the simulations presented in this paper. Due to the size of the analyzed holes and their cylindrical shape, the only method of analysing the flow through such holes is the numerical method. In the conducted simulations, the holes were D = 0.6 mm, 0.3 mm and 0.125 mm in diameter and the perforation values were equal to 4%, 5%, 8% and 10%. The L/D ratio was changed between 0.25 and 8. The data bank of the flow through the cylindrical holes was produced. The hole extension has a significant influence on the obtained mass flow rate and, consequently, on the transpiration flow efficiency. In addition, entrance effects appear to be important.

8

Aerodynamic anhancement in inner channel of turbine blade

Kaczyński P., Szwaba R., Puchowski B., Doerffer P., Flaszyński P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2015

|

Vol. 19, No 2

101--110

EN

This paper presents the numerical and experimental study of the flow structure in a radial cooling passage model of a gas turbine blade. The investigations focus on the flow aerodynamics in the channel, which is an accurate representation of the configuration used in aero engines. The flow structure and pressure drop were measured by classical measurement techniques. The stagnation pressure and velocity measurements in a channel outlet plane were performed. The investigations concerning the flow field and heat transfer used in the design of radial cooling passages are often developed from simplified models. It is important to note that real engine passages do not have perfect rectangular cross sections, but include corner fillets, ribs with fillet radii and special orientation. Therefore, this work provides detailed fluid flow data for a model of radial cooling geometry which possesses very realistic features. The main purpose of these investigations was to study different channel configurations and their influence on the flow structure and pressure losses in a radial cooling passage of a gas turbine blade.

9

Aerodynamic analysis of wind turbine rotor blades

Martinez J., Doerffer P., Szulc O., Tejero F.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2015

|

Vol. 19, No 2

129--140

EN

One of the main achievements of the PLGrid Plus project is the implementation of new tools and services designed for the numerical prediction of the aerodynamic performance of wind energy turbines. An innovative and unique integration tool (Aero-T) is aiming at automating all stages (pre-, solution and post-processing) of the numerical simulation of the flow around wind turbine rotor blades using commercial CFD software based on the RANS approach and block-structured computational grids. The FINE/Turbo package (Numeca Int.) is applied in the structured grid generation process and solution phases, while the analysis of results is left to the Tecplot 360 (Tecplot Inc.) software. A demonstrator based on the NREL Phase VI rotor experiment (conducted at NASA Ames) is introduced to prove the excellent prediction capabilities of Aero-T.

10

Innowacyjny wiatrak dla polskich warunków

Doerffer P., Doerffer K.

Czysta Energia

|

2015

|

Nr 9

38--41

11

Time-accurate simulation of flow past PZL W-3A "Sokół" (Falcon) helicopter main rotor in forward flight

Szulc O., Doerffer P., Żółtak J., Małecki J.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2013

|

Vol.17, No 1-2

43--61

EN

The paper presents the results of numerical simulations based on the URANS approach and the chimera overlapping grids technique of the main PZL W-3A "Sokół" (Falcon) helicopter rotor in forward flight conditions. The low-speed flight case models the helicopter rotor as parallel to the ground keeping forward speed of approximately 99km/h. Strong Blade-Vortex Interaction (BVI) is responsible for a high level of vibration and noise. The high-speed (266km/h) case reveals two main problems of modern helicopters: compressibility effects due to strong shock-wave boundary layer interaction on the advancing side and separation leading to a dynamic stall on the retreating side of the rotor. An attempt is made to correlate the results of the simulations with the very limited flight test data.

12

Unsteady Flow through the Gap of Savonius Turbine Rotor

Świrydczuk J., Doerffer P., Szymaniak M.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2011

|

Vol. 15, No 1

59-70

EN

The paper presents a numerical analysis of unsteady flow through the gap of a Savonius turbine rotor, performed for varying integral turbine operating parameters calculated for the case under study as well as obtained from experiments described in the literature. Changes in the unsteady flow pattern, including the development and interaction of numerous vortex structures in the vicinity of the gap, and their relevance to the varying integral parameters are discussed. We conclude that the structure responsible for the intensity of the flow through the gap is a vortex which forms in the vicinity of the gap at certain phases of rotor revolution, and that a possible way to improve the efficiency of operation of a Savonius turbine is to control the intensity of this vortex by modifying the shape of the blade edges in the vicinity of the gap.

13

Passive Control of Shock Wave Applied to Helicopter Rotor High-Speed Impulsive Noise Reduction

Doerffer P., Szulc O.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2010

|

Vol. 14, No 3

297-305

EN

A strong, normal shock wave, terminating a local supersonic area on an airfoil (or a helicopter blade), not only limits the aerodynamic performance, but also becomes a source of High-Speed Impulsive (HSI) noise. The application of a passive control system (a cavity covered by a perforated plate) on a rotor blade should reduce the noise created by the moving shock. This article describes numerical investigations focused on the application of a passive control device on a helicopter blade in high-speed transonic hover conditions to weaken the shock wave – the main source of HSI noise.

14

Numerical Simulation of Model Helicopter Rotor in Hover

Doerffer P., Szulc O.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2008

|

Vol. 12, No 3-4

227-236

EN

The article presents details of a URANS simulation of the flow field near a hovering model of the Caradonna and Tung (1981) helicopter rotor [1]. The CFD code SPARC [2] proves to be capable of capturing the aerodynamics of a two-bladed rotor in high-speed transonic hover conditions. A comparison of the simulation results with the experimental data is acceptable, hence the described methodology might be used with confidence in future numerical studies of application of noise-reducing devices on helicopter blades.

15

High-lift behaviour of half-models at flight reynolds numbers

Szulc O., Doerffer P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2006

|

Vol. 10, No 2

191-206

EN

A peniche is designed to offset a half-span aircraft model from the wind tunnel wall boundary layer. This strategy of model mounting results in large influence on the meas-ured aerodynamic coefficients, compared with full-span data, The negative influence is especially important in high-lift conditions leading to incorrect maximum lift behaviour, A very time-consuming set of python scripts was constructed to allow automatic meshing of the wing-body configuration of the DLR F11 high-lift model placed in the European Transonic Wind tunnel (ETW, Germany). Variations due to different concepts of model mountings (peniches) were included. A block-structured FLOWer solver (DLR, Germany) was used for all flow simulations, simplifying the mesh generation process by using the chimera overlapping grids technique, Preliminary results are available for a full-span configuration obtained with a symmetry condition at the mirror plane. Computations of the half-span model placed directly at the wall or mounted using a standard peniche are also presented.

16

Shock wave smearing by wall perforation

Doerffer P., Szulc O.

Archives of Mechanics

|

2006

|

Vol. 58, nr 6

543-573

EN

Normal shock wave, terminating a local supersonic area on an airfoil, not only limits aerodynamic performance but also becomes a significant source of a high-speed impulsive noise on the rotor blade of a helicopter. It is proposed to apply passive control to disintegrate the shock wave by smearing pressure gradients created by the shock. Details of the flow structure obtained by this method are studied numerically. A new boundary condition of a perforated wall is verified against experimental data for a passive control of the shock wave in a channel flow and on an airfoil. This method of shock wave disintegration is proven to work for internal flows in transonic nozzles and appears to be effective for transonic airfoils as well. The substitution of a shock wave by a gradual compression changes completely the source of the high-speed impulsive noise and bears potential of its reduction.

17

Application of the pressure sensitive paint method for transonic flow measurements

Szumski J. A., Doerffer P.

Turbulence : international journal

|

2005

|

Vol. 11

55-63

EN

Traditional measurements of the pressure distribution are conducted with use of pressure taps. Those pressure taps require model surface to be drilled through. In case of such intrusive pressure measurements the instrumentation and model mounting become a problem, especially in case of rotating compressor or turbine blades. The new optical method based on pressure (oxygen concentration) sensitive paints allow to obtain a continuous pressure distribution on the model surface in essentially non-intrusive way. The PSP technology helps understanding of the flow around the model and provides quantitative flow data for further processing. PSP method treated in this paper proved to be a very good solution for complex flows. The scope of this paper is to present the basics of the PSP method. It covers only the basic equations, general idea of the method, typical system set up and some of the approaches to PSP paint application. Typical PSP system is explained as well as the formulation of the PSP paint. The physical phenomena of the excitation, emission and oxygen quenching is explained. Deployment of the system at IFFM PAS is in the final stage, and preliminary calibration results are available. At the end of this paper the IFFM PAS plans for future, current PSP development challenges, actions to be taken, and some of the expected results are discussed.

18

Unsteady Shock Wave: Turbulent Boundary Layer Interaction in the Laval Nozzle

Doerffer P., Szulc O., Magagnato F.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2005

|

Vol. 9, No 1

115-132

EN

The flow in transonic diffusers and supersonic air intakes often becomes unsteady due to shock wave-boundary layer interaction. Oscillations may be induced by natural separation unsteadiness or forced by boundary conditions. Significant improvements of CFD tools, increased computer resources and the development of experimental methods have again drawn the attention of researchers to this topic. Forced oscillations of a transonic turbulent flow in an asymmetric two-dimensional Laval nozzle have been considered to investigate the problem. A viscous, perfect gas flow was numerically simulated using SPARC, a Reynolds-averaged compressible Navier-Stokes solver, employing a two-equation, eddy viscosity, turbulence closure in the URANS approach. For time-dependent and stationary flow simulations, Mach numbers upstream of the shock between 1.2 and 1.4 were considered. Comparison of computed and experimental data for steady states generally gave acceptable agreement. In the case of forced oscillations, a harmonic pressure variation was prescribed at the exit plane resulting in shock wave motion. Excitation frequencies between 0Hz and 1024Hz were investigated at a constant pressure amplitude. The main result of the work is the relation between the amplitude of shock wave motion and the excitation frequency in the investigated range. Increasing excitation frequency resulted in decreasing amplitude of the shock movement. At high frequencies, a natural mode of shock oscillation (of small amplitude) was observed, which was insensitive to forced excitement.

19

Numerical simulation of shock wave patterns in supersonic divergent symmetric nozzles

Namieśnik K., Doerffer P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2005

|

Vol. 9, No 1

53-63

EN

This paper presents the results of numerical simulations of supersonic flows with shock waves in a divergent symmetric nozzle of an opening angle ranging from 2 degrees to 6 degrees. At certain Mach number values the shock pattern becomes asymmetric. This asymmetry is analysed here for different values of velocity upstream of the shock wave and for different nozzle divergence angles. Only the divergent part of the nozzle is considered. Supersonic conditions at the nozzle inlet were prescribed with a chosen Mach number value Ma>1. The inlet velocity profile included a turbulent boundary layer profile on side walls. The steady flow simulation was applied for nozzle opening angles, α , of 1.877 degrees, 2.5 degrees and 3 degrees, whereas the unsteady approach was necessary for a nozzle of the divergence angle α =6.54 degrees to obtain a converged solution. The asymmetry of the shock structure is visible in the unevenness of the heights of both λ-feet. It happens at the same Mach number, at the same boundary layer and with the same geometrical constraints. This is in contradiction with our current understanding of the parameters affecting λ-foot size. The paper provides an explanation of this problem.

20

Numerical investigation of the secondary flow development in turbine cascade

Doerffer P., Rachwalski J., Magagnato F.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

|

2001

|

Vol. 5, No 2

165-178

EN

The results represent the first attempt of the numerical analysis of 3-D secondary flows formed in the linear turbine cascade wind tunnel. Numerical simulations were carried out by means of the SPRC code. It was possible to make presented here calculations thanks to the cluster of PC's providing sufficient computational resources. In order to be able to verify the obtained results the case considered is the workshop test case (D.G.Gregory-Smith 1994 Turbomachinery Workshop Test Case No.3 116). It has been shown that the obtained results are in a very good agreement with experiment. It gave confidence in the results and several important conclusions concerning the development of streamwise vortices could be made thanks to the work carried out.