Unsteady CFD Simulations of Contra-Rotating Propeller Propulsion Systems

Having proven its utility for the simulation of single rotation propellers (SRP), the unstructured DLR TAU-Code has been applied to the unsteady simulation of isolated Contra Rotating Open Rotor (CROR) congurations. In order to demonstrate the codes applicability to the simulation of the complex aerodynamics of this type of propulsion system, a generic 8x8 pusher CROR powerplant was designed and uRANS computations at typical cruise conditions of M=0.75 and an altitude of 35,000ft were performed for the two angles of attack of 0 and 2 degrees. The results obtained allow for a detailed analysis of the complex aerodynamic interactions between the two rotors as well as an in-depth analysis of the blade and rotor forces

Aeroelastic Effects in Maximum Lift Prediction of a Transport Aircraft and Comparison to Flight Data

The virtual determination of maximum lift performance of a transport aircraft configuration taking into account static aeroelastic deformations at steady-state flight conditions is described. Within the scope of the national research project HINVA (High-Lift IN-Flight VAlidation) a fluid-structure interaction approach based on high-fidelity numerical fluid dynamics and structural analysis methods has been applied to DLR’s Airbus A320- 232 ATRA research aircraft in high-lift configuration. Numerical aeroelastic analyses were performed using an in-house simulation procedure built around DLR’s flow solver TAU and the commercial finite-element analysis code NASTRAN R . Numerical results were validated against experimental data obtained from the first HINVA flight test campaign in July 2012

Aerodynamic Optimal Engine Integration for a Business Jet Configuration.

For a generic transport aircraft configuration with engines installed at the tail optimizations were performed with design parameters deforming the shape of fuselage tail, pylon and nacelle successively to assess the potential of each component. To perform the simulation based optimizations in an adequate time frame the Euler equations have been solved since comparisons with viscous flow calculations showed that transonic effects which were responsible for installation interference effects were predicted reasonably well. Finally the viscous drag of all optimized geometries, promising drag savings of nearly 5 drag counts from the inviscid calculations, were re-calculated solving the Reynolds-averaged Navier-Stokes (RANS) equations. While these final assessments also demonstrated drag savings, the predicted gain is smaller, which leads t

Numerical Simulation of a Fully Integrated Engine Ground Test

In the frame of the DLR project SAMURAI, the German Aerospace Center performed an engine ground test with an installed IAE V2527, which was accompanied by various CFD studies. One of these studies aimed at simulating the experimental set-up, including aircraft, ground and hangar with a RANS approach. Therefore, the two equation eddy viscosity model Menter SST and the Reynolds stress model SSG/LRR-g were utilized. The scope of this paper is to illustrate the numerical approach and results of this simulation. Numerical results from the jet flow were compared with measured data obtained using both a Particle Image Velocimetry and Backward Oriented Schlieren method. Regarding the velocity distributions within the outer jet shear layer, the comparison with particle image velocimetry data showed good agreement especially for the Menter SST turbulence model. However, the turbulent kinetic energy was generally overpredicted in the CFD results

The Case for Counter-Rotation of Installed Contra-Rotating Open Rotor Propulsion Systems

Contra Rotating Open Rotor (CROR) propulsion systems have seen renewed interest as a possible economic and environmentally friendly powerplant for future transport aircraft. Installation effects, i.e. the mutual interactions between airframe components and the rotors, have a pronounced impact on the aerodynamic and aeroacoustic performance for this type of engine. In this paper, the impact on aerodynamic performance and noise emissions caused by the presence of a pylon as well as a variation in the sense of rotation of the rotors is numerically studied for a representative 10x8-bladed pusher-configuration CROR engine at typical take-off conditions. In particular, the sense of rotation influence on blade and rotor performance and loadings as well as on the handling quality relevant in-plane rotor forces is analyzed, as is the resulting impact on the noise emissions in the near- and farfield and the flyover noise results. Having been widely applied to the simulations of single as well as contra-rotation propellers, the DLR CFD code TAU and the aeroacoustic analysis tool APSIM allow for a detailed analysis and an improved understanding of the complex aerodynamics and aeroacoustics of this type of propulsion system

Numerical Investigation of Unsteady Tangential Blowing at the Rudder of a Vertical Tailplane Airfoil

A numerical 2D investigation of a vertical tailplane airfoil using active flow control with tangential blowing over the rudder shoulder is conducted. The aim of the flow control application is to increase the maximum lift or side force which can be created by the vertical tailplane at critical conditions like the one engine-inoperative failure case. On the highly deflected rudder a large separation can be found without blowing. With constant tangential blowing it was shown that fully attached flow can be achieved. To increase the efficiency, pulsed blowing is applied here, leading to a similar increase in the lift coefficient at a reduced actuation mass flow required. Parameters like the blowing momentum coefficient and the dimensionless frequency are varied and the results are compared to those of the flow calculations with constant blowing. It is observed that pulsed blowing with a small momentum coefficient leads to a strong increase in the lift coefficient compared to constant blowing. The resulting lift increment depends on the dimensionless frequency selected

Experimental and Numerical Investigation of the Flow Topology During Airdrop Operations

This paper reviews experimental and numerical simulations of the dropping of simplified cargo supplies from a generic military transport aircraft carried out at DLR. Aiming at developing a well-validated process chain to accurately compute the trajectories and attitudes of airdropped cargo supplies in the proximate vicinity of the aircraft, extensive low-speed wind tunnel tests were conducted as a means to validate the numerical simu- lation. A simulation environment was established, coupling unsteady Navier-Stokes CFD methods with multi-body simulation methods, allowing for the precise computation of the time-dependent aerodynamic and ight mechanic behaviour of an airdropped supply. A comparison of selected results between the numerically simulated airdrop and the wind tunnel data is presented