Propeller Slipstream Research Articles

New actuator disk model for propeller-aircraft computation

There is a growing interest in propellers for transport aircraft as well as regional airliners from the viewpoint of energy saving. An important consideration for utilizing a propeller propulsion system on aircraft is the aerodynamic interaction between the propeller slipstream and other aerodynamic surfaces. It is therefore necessary to use a simplified but relatively accurate tool for propeller modeling, with the widely used actuator disk model. The advantage of this model is that it is easy to use and inexpensive in terms of computation time required. In addition, it also produces acceptable results. In this study, a new regionalized actuator disk model was utilized in the analysis of propeller slipstream interference effects on a real four-propeller aircraft. The results are compared with the cases of inactive actuator disks, which shows that the propeller slipstream causes an increase in the lift and drag coefficients. An evident yawing effect caused by the rotating slipstream was noticed, which should be taken into account in the design phase. The regionalized actuator disk model is evaluated as a fast and relatively accurate model for propeller preliminary design.

Preliminary Design Estimation of the V/STOL Airplane Performance

A preliminary study on estimating aerodynamic forces of a Vertical/Short Takeoff and Landing (V/STOL) mini Unmanned Air Vehicle (UAV) configuration with Distributed Electric Propulsion (DEP) system is presented. The main objective is to offer the next generation fixed wing mini UAV aircraft configuration with high-speed cruise flight and vertical take-off capabilities. The proposed concept uses four electric motors and propellers combination located on the leading edge of the wing. The described method uses semi-empirical formulations in order to estimate the forces and moments generated by the wing immersed in its distributed propeller slipstreams. Actuator disk theory is used for the propeller slipstream, where the thrust is assumed to be known for the calculations. Upwash of the fuselage and each propeller slipstream are taken into account for the wing and propeller inflow angle calculations. The resulting method, which is written as a program, serves as a conceptual design program for this type of configuration. Additionally, the program will be used for generating data for flight dynamics simulations. A candidate design is also presented, which is being manufactured for the on-going developments and tests.

A computation study on the aerodynamic influence of interaction wing-propeller for a tilt-body MAV

Purpose – The purpose of this paper is to investigate the influence of a propeller slipstream on the aerodynamic characteristics of a fixed-wing micro air vehicle (MAV) by simplifying a propeller to an actuator disk and an actuator volume. Design/methodology/approach – A computational fluid dynamic (CFD) approach. Findings – The simulation flows are found and show that the propeller slipstream changes the flow field around the wing, which improves the aerodynamic performance of the wing. The aerodynamic performance is improved first, when the separation of the boundary flow at the upper surface wing is delayed. Second, the flow region of the boundary layer is boosted close to the wing surface again at a high incidence angle. And finally, the velocity inlet of the wing is increased by the propeller-induced flow. Research limitations/implications – The incidence angle is in the range of 0-80°with an increment of 20°. The free stream velocity and RPM used are 6 m/s and 5,000 rpm, respectively. Originality/va...

비행시험과 전산해석을 통한 소형무인기 항력 예측

This paper presents the procedure of drag prediction for EAV-1, based on a numerical analysis correlated to an in-flight test. EAV-1, developed by Korea Aerospace Research Institute, is a small-sized UAV to test a hydrogen-fuel cell power system. The long-endurance test flight of 4.5 hours provides numerous in-flight data. The thrust and drag of EAV-1 during the flight test are estimated based on the wind-tunnel test results for EAV-1`s propeller performance. In addition, the CFD analysis using a commercial Navier-Stokes code is carried out for the full-scale EAV-1. The computational result suggests that the initial CFD analysis substantially under-predicts the in-flight drag in that the discrepancy is up to 27.6%. Therefore, additional investigation for more accurate drag prediction is performed; the effect of propeller slipstream is included in the CFD analysis through fan disk modelling. Also, the additional drag from airplane trim and load factor that actually exists during the flight test in a circular path is considered. These supplemental analyses for drag prediction turn out to be effective since the drag discrepancy reduces to 2.3%.

The Effect of Ship Coefficients on the Efficiency Gain f Propeller-Vane System

This paper discusses a correlation between non dimensional parameter of the ship (L/B,B/T, wake fraction, ratio between induced and advance velocity, thrust loading coefficient) and energy gain by applying vane-turbine in the propeller slipstream. The data based on the basis of statistical data (numerical) and model testing. The correlation data can be calculated by quantifying the contribution of causal variables to a targeted effect variable directly and indirectly through other variables and this would be examined by Path analysis. By using this coefficient, it is possible to demonstrate which variable has the main contribution on the efficiency gain. The Data analysis of Microsoft Office Excel software is used to approach the calculation. It is found that L/B and CT affected indirectly the efficiency gain of vane-turbine

Optimal Low-Drag Wing Planforms for Tractor-Configuration Propeller-Driven Aircraft

This paper proposes novel wing planforms that reduce induced drag by exploiting the slipstream in aircraft driven by propellers in tractor configuration. The novel planforms are determined by optimization through an extended lifting-line theory that accounts for slipstream effects and an optimizer that includes the option of using an appropriate number of Bézier polynomial weights as control parameters describing wing planform. The optimization package written for the purpose (PROWING) minimizes a user-selected cost function, subject to a wide class of geometric and mechanical constraints on such variables as root chord, tip chord, span, wing area, bounds on wing twist and chord, airfoil profiles, root bending moment, etc. A general feature of the optimal wing planforms so generated is that the chords are shorter within the slipstream and longer on either side of it. For a wing of aspect ratio 12 and prescribed wing area, PROWING predicts that an optimal planform can reduce induced drag by about 9.15%, with a maximum local wing chord variation of about 37% over a conventional reference wing. PROWING-based optimal planforms have been assessed in two ways: 1) by an Euler code that includes a blade-element theory module for the propeller and accounts for the aerodynamic effect of the propeller slipstream on wing planform; and 2) by a Reynolds-averaged Navier–Stokes simulation coupled to the blade-element theory module. Both assessments confirm that the class of planforms proposed here reduce drag but with slight differences, which is not unexpected because of the different assumptions underlying the different methods.

Development and Validation of a Propeller Slipstream Model for Unmanned Aerial Vehicles

Recent interest in high-angle-of-attack flight, aerobatic maneuvering, vertical/short takeoff and landing, etc., of small unmanned aerial vehicles necessitates more detailed modeling of the complex aerodynamics associated with these flight regimes. This includes modeling the effect of the propeller slipstream, also called prop wash, which is the main source of airflow that helps maintain lift and control during near-zero forward-speed flight like that encountered during vertical/short takeoff and landing, as well as during high-angle-of-attack flight/aerobatic maneuvering like hovering. Propeller slipstream models based on conventional theories, such as the momentum theory, have been used extensively in the literature to predict the induced air velocity within the slipstream. However, because these conventional theories consider only acceleration of air within the slipstream and not diffusion, their applicability in regions far downstream of the propeller where diffusion is dominant, is questionable. This paper presents a propeller slipstream model that considers both acceleration and diffusion within the slipstream using simple analytical and semi-empirical equations. The proposed model is shown to be in good agreement with the experimental data for several different propellers and configurations, up to propeller diameters downstream of the propeller plane, with an rms error of in velocity. As well, the proposed model matches the simplicity of conventional models and is therefore suitable for real-time applications.

Aerodynamic Effects of Propeller Slipstream on a Wing with Circulation Control

The German Bürgernahes Flugzeug (Citizen-Oriented Airplane) research program advances technologies for high-lift systems using circulation control Coandă-type flaps. The interaction of these high-lift systems with a propeller engine is the subject of the present work. A large and complex wind-tunnel model equipped with an active high-lift system and a powered propeller was designed, manufactured and instrumented. The wind-tunnel data show the potentials of the active high-lift system in three-dimensional wing applications. The results characterize and quantify the interactions between a propeller and a high-lift wing by using systematic variations of blowing momentum and propeller thrust. The results represent a unique database for future efforts to improve the efficiency of active lift and for validation of numerical simulation methods.

Numerical Investigation of Engine Effects on a Transport Aircraft with Circulation Control

The scope of this paper is to illustrate the installation effects of a turboprop engine on a high-lift configuration of a short takeoff and landing aircraft with circulation control. In addition to the influence on the wing performance, the impact on the longitudinal static stability of the aircraft is also investigated. Furthermore, critical failure cases, namely one engine inoperative, as well as an asymmetric circulation control failure, are assessed. Therefore, steady computational-fluid-dynamics calculations based on the Reynolds-averaged Navier–Stokes equations were performed. The propeller is modeled with an actuator-disk approach. The results show strong potential of increasing lift by synergy effects between circulation control and propeller slipstream. However, the longitudinal stability and controllability are adversely affected. Regarding the case of one engine inoperative, the resulting yawing moments are twice as high as the actual yawing moments from the asymmetric thrust and are therefore higher than expected.

Investigation on Different Methods for Numerical Simulation of Propeller Slipstream

In order to describe propeller slipstream interactions with other components and assess the capability and applicability of different methods in propeller slipstream simulation, the flow fields and aerodynamics of propeller/nacelle and propeller/wing models at different work status are calculated. Numerical methods used for comparisons are unsteady method in which propeller is accurately simulated with body-fitted grid and quasi-steady approach where propeller is modeled as an actuator-disk. The solver used is based on unstructured embedded grid technique and OMP parallel method, Reynolds averaged Navier-Stokes equations associated with the one-equation Spalart-Allmaras turbulence model are solved and the governing equations are discretized by a second-order upwind finite-volume scheme and dual time-stepping scheme. The results for propeller/nacelle and propeller/wing configuration in axial flow conditions, which contain the induced velocity in axial and azimuthal directions and aerodynamics obtained by different methods, are compared. Meanwhile, effect of propeller installation to wing loads under differentincidence flow angles is discussed further, and some meaningful conclusions are drawn.

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.

Minimizing Axial Energy Loss by Using Vane Turbine in the Propeller Slipstream

The paper describes the results of analytical investigation on the application of vane-turbine in the propeller slipstream. The vane-turbine is attached on single-and twin-screw ships with total number of investigated ships are 20. Performance of the turbine was analyzed by actuator disc method. The effect of vane-turbine on ship performance is investigated. Discussions are focused on two main topics, namely speed loss and power efficiency gain. Final result finds out that the ratio of the thrust-power producing by vane turbine and thrust-power producing by propeller will influence the efficiency gain.

A performance study on the energy recovering turbine behind a marine propeller

This study presents the performance estimation of a turbine, as a new concept of energy saving device (ESD), utilizing the energy in the propeller slip stream. The turbine is designed to recover the rotational energy into torque to drive a generator inside the rudder. First, the problem of performance estimation is formulated by a numerical variational method so that the turbine generates a prescribed torque with minimum propulsion power of the propeller and without loss of the required thrust of the combined system. Each component is represented by vortex lattice lifting lines and the radial distribution of circulation is determined by the solution of the problem. It is investigated how the performance of the system depends on the design parameters such as power coefficient and rotational speed of the turbine. Finally, a turbine blade is designed for a selected case using the information from the parametric study. A CFD analysis based on RANS simulation is applied to look into the flow around the turbine blade. The results of the performance calculation are also compared with the preliminary predictions.

Design, Performance and Testing of a Quad Rotor Biplane Micro Air Vehicle for Multi Role Missions

It is useful to combine hover and forward flight capability of air vehicles into a hybrid design. This paper discusses the development of one such hybrid air vehicle: Quadrotor biplane. The proof-of-concept vehicle weighs 240 grams and consists of four propellers with wings arranged in a biplane configuration. The performance of the propeller-wing was investigated in non-axial flow conditions through a systematic series of wind tunnel experiments. The effect of the wing on propeller slipstream and vice versa significantly changed the magnitude of vertical and horizontal forces when compared with the forces produced by an isolated propeller. Accounting for these effects, trim analysis showed that the maximum speed of 11 m/s at 0 deg shaft angle and a cruise speed of 4 m/s at 18 deg shaft angle was achievable. The cruise power was approximately one-third of that required for hover. Free flight testing of the proof-of-concept vehicle successfully showed feasibility of vehicle to achieve equilibrium transition flight. In order to improve performance, a few key design parameters such as airfoil profile, wing aspect ratio, biplane wing spacing and offset between propeller axis and wing chord were also experimentally investigated. It was found that a careful trade-off between efficiency and compactness affects the final choice of the design.

Twisted rudder for reducing fuel-oil consumption

Three twisted rudders fit for large container ships have been developed; 1) the Z-twisted rudder that is an asymmetry type taking into consideration incoming flow angles of the propeller slipstream, 2) the ZB-twisted rudder with a rudder bulb added onto the Z-twisted rudder, and 3) the ZB-F twisted rudder with a rudder fin attached to the ZB-twisted rudder. The twisted rudders have been designed computationally with the hydrodynamic characteristics in a self-propulsion condition in mind. The governing equation is the Navier-Stokes equations in an unsteady turbulent flow. The turbulence model applied is the Reynolds stress. The calculation was carried out in towing and self-propulsion conditions. The sliding mesh technique was employed to simulate the flow around the propeller. The speed performances of the ship with the twisted rudders were verified through model tests in a towing tank. The twisted versions showed greater performance driven by increased hull efficiency from less thrust deduction fraction and more effective wake fraction and decreased propeller rotating speed.

A numerical study of scale effects on performance of a tractor type podded propeller

In this study, the scale effect on the performance of the podded propeller of tractor type is investigated. Turbulent flow computations are carried out for Reynolds numbers increasing progressively from model scale to full scale using the CFD analysis. The result of the flow calculation for model scale Reynolds numbers agrees well with that of the experiment of a large cavitation tunnel. The existing numerical analysis indicates that the performance of the podded propeller blades is mainly influenced by the advance coefficient and relatively little by the Reynolds number. However, the drag of pod housing with propeller in operation is different from that of pod housing without propeller due to the acceleration and swirl of propeller slipstream which is altered by propeller loading as well as the pressure recovery and friction according to Reynolds number, which suggests that the pod housing drag under the condition of propeller in operation is the key factor of the scale effect on the performance between model and full scale podded propellers. The so called ‘drag ratio’, which is the ratio of pod housing drag to total thrust of podded propeller, increases as the advance coefficient increases due to accelerated flow in the slipstream of the podded propeller. However, the increasing rate of the drag ratio reduces continuously as the Reynolds number increases from model to full scale progressively. The contribution of hydrodynamic forces, which acts on the parts composed of the pod housing with propeller operating in various loading conditions, to the thrust and the torque of the total propeller unit are presented for a range of Reynolds numbers from model to full scales.

Propeller Slipstream Interference with Wing Aerodynamic Characteristics of Mars Airplane at Low Reynolds Number

Propeller Slipstream Interference with Wing Aerodynamic Characteristics of Mars Airplane at Low Reynolds Number

Regionalized Actuator Disk Model Designed by Optimization Method for Propeller Slipstream Computation

In this paper a new actuator disk model is designed with regionally distributed parameters varying along both radial and circumferential directions to improve the simulation of classical actuator disk model which loses flow reality downstream in the case of high angle of attack. Parameters of pressure jump and tangential velocity in different regions are obtained according to the idea of best fitting with optimization method. Comparisons of flow field data between regionalized actuator disk model and full blade model show that the new model offers a better agreement than classical model in the case of high angle of attack. Results of this study confirm that the regionalized actuator disk model can benefit full aircraft computation.

Vane-Turbine as an Energy Conversion in the Propeller Slipstream of Single Screw Ship

The screw propeller of a ship generates thrust to make it moving. As a propeller rotates, it draws fluid into itself from the surrounding area (slipstream). The propeller produces two types of flow behind it, accelerated and circulated flows. Some of the energy from the ship engine is lost in the accelerated flow behind ship as a jet wash.The kinetic energy losses in the slipstream propeller captured by a turbine called the propeller-turbine system. This composed screw propeller of a vessel (the main propeller) and a vane turbine that is the area of vanes located inside the wake of the main propeller. It recovers the energy generated by the main propeller pushing water back out (which would be otherwise wasted behind the main propeller) and hopefully enhancing the efficiency of the main propeller.The influence of vane turbine on the performance breakdown of single screw ships were analyzed by using 5 (five) ships . Ship powering was calculated by using DESP Code 10 software. Thrust and power of vane turbine were calculated by applying actuator disc theory. Although the vane turbine affected speed loss of the ship, the power efficiency gained to be found always positive. Vane turbine is suitable as an energy saving device of the single screw ship.

Vane-Turbine as an Energy Conversion in the Propeller Slipstream of Single Screw Ship

Vane-Turbine as an Energy Conversion in the Propeller Slipstream of Single Screw Ship