Influence of a rough surface on the aerodynamic characteristics of a rotating cylinder

The article considers the influence of the relative roughness of a cylindrical blade on aerodynamic characteristics. It is known that the operation basis of blades under consideration is the Magnus effect, which is characterized by appearance of a lifting force (Magnus force), when the cylinders rotate in a transverse flow. This force is used to rotate the wind wheel, similar to lifting force, but can have a much larger value when selecting optimal conditions, both geometric and aerodynamic. The authors conducted a comparative analysis of cylinder layout with a relative roughness (0.005 ÷ 0.02). Experimental studies of aerodynamics process of rotating cylinders were carried out in the aerodynamic laboratory using the T-1-M wind tunnel at an air flow value of 5 to 15 m/s. Graphs of dependences of rotating cylinder's lifting force and drag force on the changing air flow velocity and on relative roughness, k/d, are obtained. For further study experimental cylinder layout’s aerodynamic parameters, the most optimal is the variant with a relative roughness value of 0.02, which had high indicators, was selected. In the course of experimental studies, graphs of the dependence of the values of lift and drag force on the angles of attack of a single rotating cylinder with a rough surface on the speed and angle of attack of the wind flow (0°, 30° and 60°) were obtained. It is established that the effective angle of attack is 0°, at which aerodynamic characteristics’s maximum values were obtained.

Parabolic velocity profile causes shape-selective drift of inertial ellipsoids

Understanding particle drift in suspension flows is of the highest importance in numerous engineering applications where particles need to be separated and filtered out from the suspending fluid. Commonly known drift mechanisms such as the Magnus force, Saffman force and Segré–Silberberg effect all arise only due to inertia of the fluid, with similar effects on all non-spherical particle shapes. In this work, we present a new shape-selective lateral drift mechanism, arising from particle inertia rather than fluid inertia, for ellipsoidal particles in a parabolic velocity profile. We show that the new drift is caused by an intermittent tumbling rotational motion in the local shear flow together with translational inertia of the particle, while rotational inertia is negligible. We find that the drift is maximal when particle inertial forces are of approximately the same order of magnitude as viscous forces, and that both extremely light and extremely heavy particles have negligible drift. Furthermore, since tumbling motion is not a stable rotational state for inertial oblate spheroids (nor for spheres), this new drift only applies to prolate spheroids or tri-axial ellipsoids. Finally, the drift is compared with the effect of gravity acting in the directions parallel and normal to the flow. The new drift mechanism is stronger than gravitational effects as long as gravity is less than a critical value. The critical gravity is highest (i.e. the new drift mechanism dominates over gravitationally induced drift mechanisms) when gravity acts parallel to the flow and the particles are small.

Analysis of the Particles’ Movement Over the Flat and Profiled Rotating Discs surface in the Velocity Layer of the Viscous Gas

Experiments on the rotating in the air cones with vertex angle β = 120º and flat disc shown that on frequencies Ω ≥ 2.5 hertz exists a qualitative difference in movement for the particles with diameters d ≈ 1 mm and d ≈ 0.1 mm. The particles with d ≈ 0.1 mm move in the near-surface region, the particles with d ≈ 1 mm jump up to 3 cm. Comparison of the spherical and aspheric (ellipsoid with axles d, d and 4 /3 d) particles' kinematics moving shown the inevitability of the large particles jump occurrence. Large particles come to self-oscillation regime by reason of periodically appearance of the Magnus force. Small particles are localized in the velocity layer

Evaluation of Magnus Force on Check Ball Behavior in a Hydraulic L Shaped Pipe

This paper presents the effect of the rotational speed of a check ball in a hydraulic L-tube on the translational motion caused by the Magnus effect. A spring-driven ball check valve is one of the most important components of a hydraulic system and controls the position of the ball to prevent backflow. To simplify the structure, the springs must be eliminated. To this end, it is necessary to clarify the flow pattern of the check ball in an L-shaped pipe and the rotational and translational behaviors of the ball. In this study, the position of the inlet pipe and the availability of the check were determined using Computer Aided Engineering (CAE) tools. By moving the position of the inlet pipe from the top to the bottom of the housing, the direction of the rotation of the ball was reversed, and the behavior changed significantly. It was found that the Magnus force, which causes the ball to levitate by rotating it in the opposite direction to the flow, acts to shorten the floating time.

Effects of spin rate on the surface pressure distribution of a rotating model

A new experimental technique has been developed to measure the pressure distribution over the surface of a rotating model in a wind tunnel for various spin rates, free-stream Mach numbers, and angles of attack. In this method, all of the measuring instruments are placed inside the rotating model which eliminated previous operational limitations and technical problems associated with attempts to measure the Magnus effect. The validity and reliability of the measured data was verified by comparing the integrated surface pressure values and aerodynamic forces, with those directly measured from an internal strain gauge balance. From the acquired surface pressure data distribution of both local and total Magnus force on the model as well as the interpretation of the boundary layer and flow separation effects on the rotating model could be determined. The Magnus force distribution shows that the local Magnus force increases along the length of the model and the maximum local Magnus force occurs at the end of the projectile. The acquired experimental data were further compared with the numerical simulations and satisfactory results were achieved. This new experimental technique can be easily applied to a variety of model configurations testing at different Mach numbers, spin rates, angles of attack, etc.

Analysis of the Magnus Moment Aerodynamic Characteristics of Rotating Missiles at High Altitudes

The Magnus moment characteristics of rotating missiles with Mach numbers of 1.3 and 1.5 at different altitudes and angles of attack were numerically simulated based on the transition SST model. It was found that the Magnus moment direction of the missiles changed with the increase of the angle of attack. At a low altitude, with the increase of the angle of attack, the Magnus moment direction changed from positive to negative; however, at high altitudes, with the increase of the angle of attack, the Magnus moment direction changed from positive to negative and then again to positive. The Magnus force direction did not change with the change of the altitude and the angle of attack at low angles of attack; however, it changed with altitude at an angle of attack of 30°. When the angle of attack was 20°, the interference of the tail fin to the lateral force of the missile body was different from that for other angles of attack, leading to an increase of the lateral force of the rear part of the missile body. With the increasing altitude, the position of the boundary layer with a larger thickness of the missile body moved forward, making the lateral force distribution of the missile body even. Consequently, Magnus moments generated by different boundary layer thicknesses at the front and rear of the missile body decreased and the Magnus moment generated by the tail fin became larger. As lateral force directions of the missile body and the tail were opposite, the Magnus moment direction changed noticeably. Under a high angle of attack, the Magnus moment direction of the missile body changed with the increasing altitude. The absolute value of the pitch moment coefficient of the missile body decreased with the increasing altitude.