Jet Control of Flow Separation on Hydrofoils: Performance Evaluation Based on Force and Torque Measurements
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Jet Control of Flow Separation on Hydrofoils: Performance Evaluation Based on Force and Torque Measurements L. I. Maltsev1* , V. D. Dimitrov2 , E. M. Milanov2 , I. I. Zapryagaev1 , M. V. Timoshevskiy1 , and K. S. Pervunin1 1
Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, pr. Akad. Lavrent’eva 1, Novosibirsk, 630090 Russia 2 Bulgarian Ship Hydrodynamics Centre (BSHC), Institute of Metal Science, Equipment and Technologies “Acad. A. Balevski,” Bulgarian Academy of Sciences, William Froude str. 1, P.O. Box 58, kv. Asparuhovo, 9003 Varna, Bulgaria Received June 1, 2020; in final form, July 17, 2020; accepted July 21, 2020
Abstract—Operating characteristics of aeronautic and marine vehicles, as well as hydraulic machines designed for various purposes are largely affected by flow separation. Therefore, control of separated flows is an extremely important problem for modern aviation and marine engineering. Based on dynamometric measurements of forces and torque acting on model hydrofoils and the ship rudder, jet control of flow separation in cavitation-free and cavitation regimes at low and high angles of attack is studied. It is shown that generation of a near-wall jet can ensure a separationless flow around test models at angles of attack greater than 30 degrees. In this case, the lift coefficient of the hydrofoil can increase approximately by two or three times. Pressure fluctuations near the body and in its wake vanish due to flow stabilization; as a result, oscillations of hydrodynamic loads on the body decrease. DOI: 10.1134/S1810232820030078
1. INTRODUCTION Investigations of flow separation form one of the most important areas of fluid dynamics research. Operating characteristics of aeronautic and marine vehicles, as well as hydraulic machines designed for various purposes, e.g., pumps and hydraulic turbines, are largely affected by flow separation. Flow separation control offers a possibility of significant enhancement of the lift coefficient of the aircraft wing or hydrofoil, which is extremely important in particular, at the beginning of vehicle motion or at reaching critical angles of attack. Hydrofoil ships were widely used in the second half of the last century all over the world and especially in the USSR. For various reasons, the interest to hydrofoil ships is less pronounced at present. Nevertheless, specialists believe that the hydrofoil ship (HS) development will be revived in the next two decade because, e.g., short-distance ferry and passenger transport will be mainly provided by ships of this type [1, 2]. Obviously, the predictions of the further engineering progress for hydrofoil ships are based on modern achievements in the development of new-type hydrofoils and superhighpower engines. One of the most realistic methods of improving HS efficiency is to increase the lift force of the hydrofoil, which is associated with the growth of the relative thickness of the hydrofoil, expansion of its angles of attack, and, hence, elevated risk of flow separation. One of the most famous and wel
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