Oskar Szulc

Application of the passive control of shock wave to the reduction of high-speed impulsive noise

Strong, normal shock wave, terminating a local supersonic area on an airfoil (or helicopter blade), not only limits aerodynamic performance but also becomes a source of a high-speed impulsive (HSI) noise. The application of a passive control system (a cavity covered by a perforated plate) on a rotor blade should reduce the noise created by a moving shock. This article covers details of the numerical implementation of the Bohning/Doerffer transpiration law into the SPARC code and includes a validation against the experimental data obtained for the ONERA transonic nozzle with a flat wall. The passive control device is then applied numerically on a helicopter blade in high-speed transonic hover conditions to weaken the shock wave – the main source of HSI noise.

Improvement of Wind Turbine Blade Performance by Means of Rod Vortex Generators

Wind turbines are complex energy conversion fluid-flow machines which entail coupled aero-mechanical issues. From an aero-acoustical point of view, wind turbine blades present two main problems: first, a reduced aerodynamic performance due to flow separation, and second, the level of noise emissions. Flow separation appears on the blade as a result of high angles of attack causing a decrease in the aerodynamic efficiency. In this chapter, the application of rod vortex generators (RVGs) to control and decrease the flow separation—by the creation of streamwise vorticity on the blade—is presented. The NREL Phase VI wind turbine rotor and the S809 airfoil are used as reference cases. The validation of NREL Phase VI model rotor against experimental data is found to be satisfactory. A study into the effects of RVGs’ chordwise location and spanwise distance is presented for selected cases and a range of inflow conditions. It is shown that the proposed RVGs lead to an improvement of the aerodynamic performance, and can be successfully applied by the wind energy industry.

Numerical Simulation of Airflow and Acoustic Field Around a Passenger Car Model Using Euler Approach and Hybrid Meshing

This chapter summarizes the results of a combined numerical analysis of airflow and associated acoustic field for a passenger car. The solution model was based on a simplified inviscid approach (Euler equations). In contrast, a full, complex shape of Nissan 350z was implemented in the simulation, based on the hybrid meshing methodology. The initial process of preparation of the surface CAD model, including the procedure of closing the gaps (necessary to assure that the body is watertight), is described. The details of the unstructured/hybrid mesh generation phase are supplemented as well. The fluid flow model was extended by the acoustic box refinement, designed to support sound wave propagation up to a frequency of 5 kHz. Steady solution at forward velocity V of 100 km/h is presented. Unsteady simulations allow for identification of many known sources of the aerodynamic noise within a low-frequency part of the acoustic pressure fluctuation spectrum, attributed to specific components of the car shape. Described method may be used for various flow configurations, including the effect of new flow control devices (currently investigated experimentally and numerically at IMP PAN) on acoustic signature.

Implementation of Rod Vortex Generators on Helicopter Rotor Blades in Hover and Forward Flight Conditions

This chapter describes the possible application of Rod Vortex Generators (RVGs) on helicopter rotor blades. Two different flight conditions are considered: hover and forward flight. The numerical model is validated with the available experimental data of the Caradonna–Tung model helicopter rotor blade (hover conditions) and the AH-1G helicopter (forward flight conditions). The application of RVGs on both rotor blades leads to an increment of the thrust coefficient with a power consumption penalty

Investigation of Vortex Generators on Channels and Airfoils

The chapter describes two different passive flow control devices (air-jet vortex generators (AJVGs) and rod vortex generators (RVGs)) and their possibilities to induce streamwise vortices and to control and reduce flow separation. For each strategy, a validation of the numerical model is performed by direct comparison of numerical results and measurements of different flow conditions: subsonic (M = 0.3) and supersonic (M = 1.43). The present investigations have been carried out for two flow cases. Firstly, a basic study of the creation and development of the streamwise vortex in space was performed. It consisted in one single vortex generator enclosed in a flat wall nozzle. Secondly, an array of 16 vortex generators were placed on a curved wall nozzle with negative pressure gradient (trying to mimic similar flow conditions as for airfoils or helicopter rotor blades), and the influence on the flow separation was studied. Besides, the implementation of vortex generators on airfoils is investigated, and their impact on the aerodynamic performance is quantified.

Experimental and Numerical Database of EU Research Projects Investigating Shock Wave-Boundary Layer Interaction in Transonic/Supersonic Flows

One of the achievements of the PLGrid Plus project is the development of a new web service called “Projects’ Database” (pol. Baza Danych Projektowych “BDP”) located at https://bdp.plgrid.pl within the PL-Grid Infrastructure. The service is designed as a unique medium for sharing the experimental and numerical results obtained during European research projects related to shock wave-boundary layer interaction and its control in transonic/supersonic flows. User access to valuable data is granted and managed through PL-Grid mechanisms and Open ID authorization allowing for an extensive validation of new physical models, advanced numerical methods and Computational Fluid Dynamics (CFD) codes applied to shock wave-boundary layer interaction phenomenon.