Hamid Reza Shahifar, Hassan Ghasemi,
Volume 3, Issue 4 (9-2006)
Abstract
When the body is running at fully immersed condition in viscous fluid, there are two components of resistance, i.e. frictional resistance and form drag. When it is near the free surface, the additional drag encountered to the body which is wave-making drag. This paper is presents the hydrodynamic performance of high-speed Unmanned Underwater Vehicle (UUV) in fully immersed condition. We did 1000000 (cells) fluid mesh around the body using Navier Stokes (N-S) equations and appropriate boundary conditions. The calculations of drag and lift have been obtained at various speeds and attack angle. The model is used to solve the N-S equations. We firstly calculated for the sphere and the results of pressure distributions and drag are very good and satisfactory with the experimental data. The calculations are extended to the UUV and the pressure distributions and drag are shown in good agreement with data.
Hassan Ghasemi, Ahmad Reza Kohansal,
Volume 5, Issue 10 (3-2010)
Abstract
In this study, the boundary element method is formulated to evaluate hydrodynamic characteristics of bodies including free surface effect. The method is based on two equations, the perturbation potential boundary integral and the pressure Kutta condition, which are solved simultaneously. The method uses isoparametric elements for both quantity and geometric on the boundary. The method is first applied to two three-dimensional bodies (hydrofoil and vertical strut) of the NACA4412 profiles and symmetric Joukowski with 12% thickness. It is assumed that hydrofoil moves in constant speed. Some results of the pressure distribution, lift, wave-making drag and wave pattern are presented. It is shown that the computational results are in good agreement with the experimental measurements and other calculated values.
Dr Hamid Zeraatgar, Ehsan Hassani Chalaksara, Reza Yousefnejad, Mohammad Javad Javaherian,
Volume 8, Issue 15 (10-2012)
Abstract
Analysis of wedge water entry as a basic problem has wide application. Model testing is a powerful means to deal with the said problem. In this study, a set of water entry tests on wedges of 20, 30 and 40 degrees deadrise angles has been conducted and the pressure distributions are recorded. Free falling method in symmetry conditions are considered in this research. A parametric study on pressure coefficients due to velocity and deadrise angles has been carried out on the wedge. Furthermore, Z-parameter as a non-dimensional factor defined for two individual parameters, time and depth of entry, has been evaluated. Finally, some comparison with numerical methods is presented. The kind of parametric study by means of model test may be regarded as the outcome of this study.
