On the calculation of the pressure drag coefficient of a flat plate using the law of conservation of energy

Abstract

Abstract The article concerns the development of a new physical model for calculating the pressure resistance of a normal-oriented thin flat plate moving in incompressible fluid. The proposed “displacement-inflow” model uses the minimum number of assumptions of fundamental nature (the law of conservation of energy, the continuity condition, no viscosity). The main idea consists in calculating the increment of kinetic energy by fluid particles both before and after the plate at each discrete step of motion. The proposed approach made it possible to estimate the contribution of the front and back surfaces of the plate to the total pressure resistance of the plate separately. Thus, the pressure drag coefficient of the front side is equal to 1.0, of the back side – 0.33 for linear approximation of the velocity profile (0.20 for the quadratic approximation), so the total drag coefficient is 1.33 (or 1.20), which is very close to the reported experimental data. The obtained partial resistance coefficients for each surface of the plate allow us to use them for calculating the resistance forces and moments acting on a vessel hull. An example of such a calculation is given.