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Effects of boundary layer control method on hydrodynamic characteristics and tip vortex creation of a hydrofoil

Ghadimi P., Araz-Tanha A., Nemati-Kourabbasloo N., Tavakoli S.

Polish Maritime Research

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2017

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nr 2

27--39

EN

There is currently a significant focus on using boundary layer control (BLC) approach for controlling the flow around bodies, especially the foil sections. In marine engineering this is done with the hope of increasing the lift – to – drag ratio and efficiency of the hydrofoils. In this paper, effects of the method on hydrodynamic characteristics and tip vortex formation of a hydrofoil are studied. Steady water injection at the tip of the hydrofoil is simulated in different conditions by using ANSYS-CFX commercial software. Validity of the proposed simulations is verified by comparing the obtained results against available experimental data. Effects of the injection on the lift, drag, and lift – to – drag ratio are studied and the ranges within which the injection has the most positive or negative effects, are determined. Furthermore, flow pattern and pressure variation are studied upon the water injection to determine the most positive and negative case and to ascertain the main reasons triggering these phenomena.

2

Calm water performance of hard-chine vessels in semi-planing and planing regimes

Ghadimi P., Tavakoli S., Dashtimanesh A.

Polish Maritime Research

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2016

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nr 4

23--45

EN

In the current paper, a mathematical model is developed for performance prediction of hard-chin boats which can be used in both semi-planing and planing regimes. The proposed model bases on the 2D+T theory and implements pressure distributions over the length of the hull in order to compute the forces. To determine the forces in the semiplaning range, a function is proposed for the non-dimensional length at which the transom effect appears. Three drag components, which are: frictional drag, induced drag, and spray drag, are considered in the computations performed using an iterative method to satisfy two equilibrium equations. The validity of the proposed method is verified by comparing the predicted trim angle and resistance against the available experimental data. Based on this comparison, it is observed that the proposed method reveals satisfying accuracy in both semi-planing and planing regimes. The method is then used to study variation of hydrodynamic and hydrostatic forces as the hull makes a transition from the semi-planing regime to the planing regime. In addition, different components of the resistance are analyzed.

3

Potential Field, Geoelectrical and Reflection Seismic Investigations for Massive Sulphide Exploration in the Skellefte Mining District, Northern Sweden

Tavakoli S., Dehghannejad M., García Juanatey M. d. A., Bauer T. E., Weihed P., Elming S.-A.

Acta Geophysica

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2016

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Vol. 64, no. 6

2171--2199

EN

Multi-scale geophysical studies were conducted in the central Skellefte district (CSD) in order to delineate the geometry of the upper crust (down to maximum ~ 4.5 km depth) for prospecting volcanic massive sulphide (VMS) mineralization. These geophysical investigations include potential field, resistivity/induced polarization (IP), reflection seismic and magnetotelluric (MT) data which were collected between 2009 and 2010. The interpretations were divided in two scales: (i) shallow (~ 1.5 km) and (ii) deep (~ 4.5 km). Physical properties of the rocks, including density, magnetic susceptibility, resistivity and chargeability, were also used to improve interpretations. The study result delineates the geometry of the upper crust in the CSD and new models were suggested based on new and joint geophysical interpretation which can benefit VMS prospecting in the area. The result also indicates that a strongly conductive zone detected by resistivity/IP data may have been missed using other geophysical data.