![]() It is evident that the pressure coefficient is at its highest across all three Reynolds numbers when the angle is 0. ![]() The angle represents the specific position or angle on the cylinder wall. The pressure-coefficient plots illustrate how the pressure changes as the fluid moves across the surface of the cylinder. Pressure coefficient comparisons among Re = 1, Re = 100 and Re = 1 × 10 6 This results in a net pressure acting on the cylinder known as pressure drag, which mainly dominates the drag for high Reynolds number. The pressure in the rear of the cylinder, where the wake is present, is relatively low, whilst at the front of the cylinder it is high. The late separation of the flow occurs in Re = 1 × 10 6 due to the fact that the momentum induced by high Reynolds number and turbulent flow is much higher than that in the laminar flow, and thereby, it takes a longer distance for the adverse pressure to balance the momentum and subsequently the flow separation. This is because the separation points occur much earlier in Re = 100 comparing with the Re = 1 × 10 6 case. The size of wake region yielded by Re = 100 is much larger than that in Re = 1 × 10 6. The airflow is randomly distributed inside the wake region. The wake region can be observed at the back of the cylinder at Re = 100 and Re = 1 × 10 6. Once the airflow velocity reduces to zero, the adverse pressure gradient causes flow separation to occur. The adverse pressure gradient causes the airflow to decelerate. With the airflow passing further across the cylinder, the pressure drops to nearly zero, and the pressure gradient changes from negative (favourable gradient) to positive (adverse gradient). The maximum airflow velocity occurs at roughly 90° of the cylinder, in which the pressure is minimum. When the airflow develops around the cylinder surface, the stagnated airflow begins to increase from the stagnation point, and the boundary-layer pressure decreases to maintain the conservation of energy. When the 12-CPU is used, the speed-up is up to 2.5 times(automatic mode) and 3.5 times(manual mode) than when the 3-CPU is used.Īt the front of the cylinder (0 degree), the flow impacts on the cylinder at the stagnation point, in which the pressure is maximum but the velocity is zero. The comparisons of the speed-up for each case, for example type of cut-paste algorithm and computer systems, are shown in figure 5(b). Even with the heavy inertia of the store, the store shows a pitch-up tendency. In figure 5(a), the normal force, axial force and moment coefficients are shown, as well as the trajectory of the store. ![]() Since the store is aerodynamically unstable (this is true for any two-dimensional body), it would pitch up, experience increase in lift, and eventually collide with the airfoil. The local angle of attack of the store increases as the store separates from the airfoil. The time used here is non-dimensionalized with the chord length of airfoil( c) and the speed of sound ( a), that is t* = ta/c. Otherwise, the simulation would be terminated prematurely due to the collision of the store with the airfoil. The mass and moment of inertia of the store are chosen to be large compared to the aerodynamic forces and moments of the store ( m/ ρ ∞ L 3 = 10, I y/ ρ ∞ L 5 = 10). ![]()
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