Influence Of Propeller Slipstream Research Articles

Influence of Propeller Slipstream on the Flow Field of S-Shaped Intake

For turboprop engine, the S-shaped intake affects the engine performance and the propeller is not far in front of the inlet of the S-shaped intake, so the slipstream inevitably affects the flow field in the S-shaped intake and the engine performance. Here, an S-shaped intake with/without propeller is studied by solving Reynolds-averaged Navier-Stokes equation employed SST k-ω turbulence model. The results are presented as time-averaged results and transient results. By comparing the flow field in S-shaped intake with/without propeller, the transient results show that total pressure recovery coefficient and distortion coefficient on the AIP section vary periodically with time. The time-averaged results show that the influence of propeller slipstream on the performance of S-shaped intake is mainly circumferential interference and streamwise interference. Circumferential interference mainly affects the secondary flow in the S-shaped intake and then affects the airflow uniformity; the streamwise interference mainly affects the streamwise flow separation in the S-shaped intake and then affects the total pressure recovery. The total pressure recovery coefficient on the AIP section for the S-shaped intake with propeller is 1%-2.5% higher than that for S-shaped intake without propeller, and the total pressure distortion coefficient on the AIP section for the S-shaped intake with propeller is 1%-12% higher than that for the S-shaped intake without propeller. However, compared with the free stream flow velocity ( Ma = 0.527 ), the influence of the propeller slipstream belongs to the category of small disturbance, which is acceptable for engineering applications.

Investigation on Propeller Slipstream by Using an Unstructured Rans Solver Based on Overlapping Grids

AbstractBased on unstructured hybrid grid and dynamic overlapping grid technique, numerical simulations of Unsteady Reynolds Averaged Navier-Stokes equations were performed and investigation on isolated propeller aerodynamic characteristics and effects of propeller slipstream on turboprops were undertaken. The computational grid consisted of rotational subzone of propeller and stationary major-zone of aircraft, and walls criterion was used in the automatic hole-cutting procedure. Distance weight interpolation and tri-linear interpolation were developed to transfer information between the rotational and stationary subzones. The boundaries of overlapping grids were optimized for fixed axis rotation. The governing equations were solved by dual-time method and Lower Upper-Symmetric Gauss-Seidel method. The method and grid technique were verified by isolated propeller configuration and the computational results were in well agreement with the experimental data. The grid independence was studied to establish the numerical results. Finally, the flow around a turboprop case was simulated and the influence of propeller slipstream was presented by analyzing the surface pressure contours, profile pressure distribution, vorticity contours and profile streamline. It's indicated that the slipstream accelerates and rotates the free stream flow, changing the local angle of attack, enhancing the downwash effects, affecting the pressure distribution on wing and horizontal tail, as well as increasing the drag coefficient, pitching moment coefficient and the slope of lift coefficient.

Influence of propeller slipstream on vortex flow field over a typical micro air vehicle

ABSTRACTAn experimental study has been carried out to explore the effect of propeller-induced slipstream on the vortex flow field on a fixed-wing Micro Air Vehicle (MAV). Experiments were conducted at a freestream velocity of 10 m/s, corresponding to a Reynolds number based on a root chord of about 1.6 × 105. Surface flow topology on the surface of the MAV wing at propeller-off and propeller-on conditions was captured using surface oil flow visualisation at four angles of incidence. The mean off-body flow over the MAV was documented in the four spanwise planes at different chord position using Stereoscopic Particle Image Velocimetry (SPIV) technique at angle-of-attack of 24° for both conditions. The oil flow visualisation showed minimal differences in flow patterns for propeller-off and propeller-on conditions at 10° and 15° incidence. The small asymmetry between port and starboard side observed at 20° during the propeller-off condition became significantly pronounced at 24°. The fuselage stub which is necessary for housing the motor of the propeller was seen to have a significant effect on the flow symmetry at large incidences that can occur when the MAV encounters sudden vertical gusts. Switching on the propeller restored the symmetry at both incidences. SPIV measurements were carried out at the incidence of 24° which exhibited the highest asymmetry. The off-body data shows the re-establishment of symmetry during propeller-on condition owing to the increase in the magnitude of spanwise and vertical velocities as a result of the propeller slipstream. The findings emphasise the importance of considering the propeller flow and design of the motor housing while evaluating the aerodynamics of low-aspect-ratio MAVs.

Numerical Simulation Study on Propeller Slipstream Interference of High Altitude Long Endurance Unmanned Air Vehicle

In this paper,thecontrol equation of Multiple Reference Frame(MRF) as the propeller calculation model was present and analyzed, the propeller slipstream interference on HALE UAV was studied with three-dimensional numerical simulation. It is shown that the flow field of the MRF model is good consistent with true propeller flow, and MRF can accurately simulate aerodynamic interference on the aircraft. The stream traces on the V-tail surface were deflected and shrank, pressure distribution,Cmx and Cmzon V-tail surface was changed apparently too.Butslipstream had little effect on wing. The influence of propeller slipstream on the aerodynamic performance of the UAV at the status of taking off is biggest, become weaker at status of climbing and smallest at the status of cruising. The influence of propeller slipstream is enhanced with increment of propeller thrust and basically familiar in the same thrust between the two blade attack angle. The pressure drag on aft of UAV fuselage increased rapidly by the interference of propeller slipstream, leading aerodynamic performance of UAV become badly.

Numerical Study of Propeller Slipstream Based on Unstructured Dynamic Overset Grids

The propeller slipstream is numerically simulated by solving three-dimensional unsteady Euler equations. The method of unstructured overset grids is applied to the simulation of relative motion between the propeller and airframe. The rotationalmotion of the propeller is simulated by establishing a rotational subzone, and the airframe is contained in the stationary subzone. During the unsteady simulation with the rotational subzone rotating, there is always an overlapping area between the rotational and stationary subzones, and the overlapping area is used to convect the flow variables of the two subzones. The governing equations are solved by using the dual-time method and standard explicit four-stage Runge-Kutta method. The unsteady flowfields of different working conditions are calculated, and the influence of propeller slipstream is analyzed. Some calculating results are compared with experimental data, and they have a good agreement with each other. It is demonstrated that the present method is efficient and robust for the simulation of an unsteady propeller slipstream flow.

Propeller Slip-Stream Model in Subsonic Linearized Potential Flow

A model has been developed for computation of the time-averaged subsonic flowfield over a nacelle and a wing induced by a propeller. The slip-stream model is based on a classical propeller theory and is included in an existing panel program. The geometry of the slip stream is determined by the nacelle. The influence of the propeller is given by a combined momentum-blade element theory. No experimental data is necessary. The computed pressures and velocities are compared to wind-tunnel data for two angles of attack and two geometries: 1) an axisymmetric nacelle and wing, and 2) a nonaxisymmetric nacelle and wing. HE prediction of the influence of propeller slip stream on the flow is important in the design phase of a new propeller-driven aircraft. The flow pattern over the nacelle and wing is affected considerably by a tractor propeller mounted on the wing, particularly at take-off conditions. Panel methods are a standard tool for aerodynamical computations around three-dimensional configurations at subsonic speeds, see Ref. 1. Usually panel programs are written to solve potential flow problems but they can be amended to also handle the vortical flow behind a rotating propeller. The advantage of panel methods is that they are easy to use and inexpensive in terms of CPU time. When a propeller slip-stream capability is added to a panel program the extension should also have these two properties. The flow in the slip stream is much more complicated than ordinary freestream flow and simplifications in the computational model are necessary. Therefore, we cannot expect to obtain the same accuracy in the predictions with the slip stream as we are used to without the slip stream. This is also true for wind-tunnel experiments. In this article we describe a propeller slip-stream model which has been incorporated in an existing panel program.2 The time-averaged flow behind the propeller is generated by a system of vortices following a classical propeller theory.3 The strength of the vortices is determined by a combined momentum-blade element theory. The propeller data needed in the simulation are the number of blades, the geometry of the blades, the speed of revolution, etc. No supporting windtunnel experiment is necessary. The geometry of the slip stream is approximated taking the surface of the nacelle into account. This is important in order to obtain realistic pressures on the nacelle. The velocities in the slip stream determined by the model are introduced together with the freestream as onset flow in the panel method. The computed pressures and velocities are compared to wind-tunnel measurements from the FFA.4'5 The configuration geometries are an axisymmetric nacelle with a wing5 and a nonaxisymmetric nacelle with a wing.4 The nonaxisymmetric nacelle is such that the shape of the innermost sections of the slip stream is changed by the presence of the nacelle. The Mach number is 0.15 and the angle-of-attack a is 0 or 5 deg.