Prediction of the unsteady ventilated partial cavities

Volodymyr Semenenko,Olena Naumova

doi:10.20535/2521-1943.2020.0.212048

Volodymyr Semenenko, Olena Naumova

Open Access

https://doi.org/10.20535/2521-1943.2020.0.212048

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Abstract

Approximate methods of computing the unsteady ventilated partial cavities created on both the plane and the cylindrical streamlined surfaces have been developed. The cases of plane partial cavities past a slender wedge-shaped cavitator, and axisymmetric partial cavities past a ring flange on the surface of an infinite circular cylinder are considered. Results of computer simulation of the unsteady ventilated partial cavities of both that types are shown. A comparison of the unsteady behavior of plane and axisymmetric ventilated partial cavities is given. A comparative analysis of two methods of controlling the partial cavities by varying the cavitator shape and by regulating the gas supply rate into a cavity is given. It has been shown that the first method is more effective for a partial cavity on a plane. For an axisymmetric partial cavity on a cylinder, both the control methods appear ineffective.

Highlights

One of the ways to reduce the viscous drag of surface ship and underwater vehicle motion is to create elongated cavities on the streamlined surfaces [1]
We have developed the rapid computational algorithms that allow us to observe the behavior of unsteady cavities on a computer screen directly during calculation, i.e. to realize computer simulation
Basing on results of a series of experiments [12], we proposed the semi-empirical formula for the volumetric gas loss rate when a ventilated cavity is closed on a cylindrical body: Qout where b is the empiric coefficient which weakly depends on

Summary

Introduction

One of the ways to reduce the viscous drag of surface ship and underwater vehicle motion is to create elongated cavities on the streamlined surfaces [1]. The aim of this work is to develop approximate methods for calculating and computer simulation of unsteady ventilated partial cavities on plane and cylindrical surfaces under various unsteady perturbations, and with various methods of the cavity control. To calculate axisymmetric partial cavities on a cylinder, an approximation method based on the principle of independence of cavity section expansion by G.V.Logvinovich [5,6,7] was used. Using both the methods, we have developed the rapid computational algorithms that allow us to observe the behavior of unsteady cavities on a computer screen directly during calculation, i.e. to realize computer simulation.

Solution of plane problem

Calculation algorithm

Solution of axisymmetric problem

Conclusion

Расчет нестационарных вентилируемых пристенных каверн

Розрахунок нестаціонарних вентильованих пристінних каверн