Witold Elsner
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View article: Sensitivity analysis of wavy wall performance in turbulent separation control: Effects of amplitude and period variations
Sensitivity analysis of wavy wall performance in turbulent separation control: Effects of amplitude and period variations Open
The influence of transversely oriented sinusoidal wall corrugation on an incompressible isothermal flow in the near-wall region, subjected to adverse pressure gradient conditions at a friction Reynolds number of $Re_{\tau} = 2500$, is inve…
View article: Hot-wire spatial resolution issues in adverse pressure gradient turbulent boundary layers
Hot-wire spatial resolution issues in adverse pressure gradient turbulent boundary layers Open
The effect of a finite length of hot-wire probe sensor length on the measured streamwise velocity fluctuations is well understood in canonical wall-bounded flow, where the small-scale energy has been found to be universal and invariant wit…
View article: Numerical analysis of novel wavy wall based control of turbulent boundary layer separation
Numerical analysis of novel wavy wall based control of turbulent boundary layer separation Open
In this work, a comprehensive insight into the new passive flow control method, i.e. a two-dimensional streamwise waviness (recently proposed by Dróżdż et al. [1]) is provided using Large Eddy Simulations. This approach was demonstrated to…
View article: Experimental study of a separated shear layer transition under acoustic excitation
Experimental study of a separated shear layer transition under acoustic excitation Open
The paper discusses experimental results on the effect of broadband acoustic excitation on laminar-to-turbulent transition in a separated shear layer developing on a flat plate subjected to an adverse pressure gradient (APG) and freestream…
View article: Effect of the angle of attack on the flow around two non-identical-height square buildings in tandem arrangement
Effect of the angle of attack on the flow around two non-identical-height square buildings in tandem arrangement Open
The paper investigates the flow around two non-identical height buildings, each with the same square cross-section, arranged in tandem using a particle image velocimetry technique. Fixed gap spacing between objects G=1.5D (where D is the s…
View article: Numerical study of an acoustic field effect on boundary layer transition mechanism
Numerical study of an acoustic field effect on boundary layer transition mechanism Open
The laminar-to-turbulent transition mechanism is fundamentally important for the concepts aiming at reducing CO2 emissions and noise pollution. This research is focused on understanding the acoustic excitation effect on the transition mech…
View article: Convection velocity in turbulent boundary layers under adverse pressure gradient
Convection velocity in turbulent boundary layers under adverse pressure gradient Open
The convection velocity (UC) of turbulent structures has been studied in adverse-pressure-gradient (APG) turbulent boundary layers (TBLs) for a wide range of Reynolds numbers Reτ≈1400−4000. The study is based on estimation of the convectio…
View article: Convection Velocity in Turbulent Boundary Layers under Adverse Pressure Gradient
Convection Velocity in Turbulent Boundary Layers under Adverse Pressure Gradient Open
The convection velocity ($U_C$) of turbulent structures has been studied in adverse-pressure-gradient (APG) turbulent boundary layers (TBLs) for a wide range of Reynolds numbers $Re_τ= 1400 - 4000$. The study is based on estimation of the …
View article: Effect of the upstream cylinder shape on the flow around the downstream rectangular object in tandem configuration
Effect of the upstream cylinder shape on the flow around the downstream rectangular object in tandem configuration Open
The paper presents an experimental investigation of air flow around bluff bodies in tandem configurations. The first one concerns two square cylinders and in the second one a triangular cylinder was used as an upstream object. Experiment w…
View article: Experimental analysis of the impact of an acoustic excitation on a separated boundary layer behaviour
Experimental analysis of the impact of an acoustic excitation on a separated boundary layer behaviour Open
The paper examines the effect of acoustic excitation at broadband frequency range (100 - 650 Hz) on separated boundary layer developing on a flat plate subjected to an adverse pressure gradient. The experiment was conducted with a low inle…
View article: Experimental and numerical studies of turbulent flows over two-dimensional and three-dimensional rough surfaces under an adverse pressure gradient
Experimental and numerical studies of turbulent flows over two-dimensional and three-dimensional rough surfaces under an adverse pressure gradient Open
The effects of surface roughness and other surface topographical feature on turbulent boundary layer (TBL) development have been widely explored, especially for flow cases with a constant streamwise pressure gradient distribution. In the c…
View article: Physics of Acoustic Excitation on Boundary Layer Development
Physics of Acoustic Excitation on Boundary Layer Development Open
In such a complex system as a modern turbofan engine, the laminar boundary layers developing on surfaces of turbine blades are exposed to strong perturbations caused by acoustic waves.A high concentration of acoustic energy inside such an …
View article: Application of the diagnostic plot in estimation of the skin friction in turbulent boundary layer under an adverse pressure gradient
Application of the diagnostic plot in estimation of the skin friction in turbulent boundary layer under an adverse pressure gradient Open
The paper concerns the problem of determining friction velocity in wallbounded flows affected by an adverse pressure gradient (APG). In the work of Niegodajew et al. [22] the corrected Clauser chart method (CCCM) for such flow conditions w…
View article: Effect of Reynolds number on turbulent boundary layer approaching separation
Effect of Reynolds number on turbulent boundary layer approaching separation Open
The effect of Reynolds number on turbulent boundary layer under adverse pressure gradient has been barely investigated in the available literature. So far, experimental or numerical research on that issue were performed either for low Re o…
View article: Effective use of the streamwise waviness in the control of turbulent separation
Effective use of the streamwise waviness in the control of turbulent separation Open
It is commonly known that for a sufficiently high Reynolds number, for flow over a rough surface and other previously examined wall topologies, turbulent boundary layer separation generally occurs earlier, and the separation bubble is noti…
View article: A description of turbulence intensity profiles for boundary layers with adverse pressure gradient
A description of turbulence intensity profiles for boundary layers with adverse pressure gradient Open
The paper presents an extension of the diagnostic-plot scaling (Alfredsson et al., 2012) of the turbulence-intensity profiles for the outer region of adverse-pressure-gradient (APG) turbulent boundary layers (TBLs). An extended formula inc…
View article: Power Plant Optimisation—Effective Use of the Nelder-Mead Approach
Power Plant Optimisation—Effective Use of the Nelder-Mead Approach Open
This paper demonstrates the use of a combined software package including IPSEpro and MATLAB in the optimisation of a modern thermal cycle. A 900 MW power plant unit (operating at ultra-supercritical conditions) was considered as the study …
View article: Problems with identification of vortex rings when using anemometry measurements.
Problems with identification of vortex rings when using anemometry measurements. Open
Measurement of key vortex rings properties with the use of anemometry techniques is not so straightforward due to the angular dispersion of these structures and in consequence change of their trajectories as they move downstream. Owing to …
View article: Effect of Cylindrical Turbulators on the Mixing Process in Basic Venturi Gas Mixer Using OpenFOAM
Effect of Cylindrical Turbulators on the Mixing Process in Basic Venturi Gas Mixer Using OpenFOAM Open
This study was devoted to improving the mixing quality in a Venturi gas mixer. It is well known that the performance of industrial gas engines strongly depends on the quality of air and fuel mixture and therefore on its homogeneity. Incorr…
View article: Skin Friction Estimation in Adverse Pressure Gradient Boundary Layers Using Corrected Clauser-Chart Method
Skin Friction Estimation in Adverse Pressure Gradient Boundary Layers Using Corrected Clauser-Chart Method Open
Estimation of the wall skin friction in a turbulent boundary layer (TBL) is always challenging due to the large gradient of mean velocity in the near-wall region and requires precise measurements of mean velocity in viscous s... | Find, re…
View article: Passive Skin Friction Control Near Turbulent Separation – Preliminary Results
Passive Skin Friction Control Near Turbulent Separation – Preliminary Results Open
The paper deals with experimental analysis of passive skin friction control method applied for a high Reynolds number turbulent boundary layer close to separation. A proposed new method is based on the mechanism of scale interaction observ…
View article: Skin friction estimation in a strong decelerating flow
Skin friction estimation in a strong decelerating flow Open
The paper presents the analysis of the turbulent boundary layer developed on a flat plate subjected to an Adverse Pressure Gradient (APG) and approaching separation. The aim of the study is to examine the effects of pressure gradient on a …
View article: Study of Reynolds number effect on turbulent boundary layer near the separation
Study of Reynolds number effect on turbulent boundary layer near the separation Open
The paper deals with the experimental analysis of strong decelerated turbulent boundary layer developed on a flat plate. The special design of the test section equipped with perforated, movable upper wall allow to generate on the bottom wa…