A wind-tunnel boundary-layer study of the effects of a surface roughness change: Rough to smooth

1978 ◽  
Vol 15 (1) ◽  
pp. 3-30 ◽  
Author(s):  
P. J. Mulhearn
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Wind Tunnel ◽  
Roughness Change

Some Observations on dr. Coleman's Comments

1957 ◽  
Vol 61 (557) ◽  
pp. 361-361
Author(s):  
G. V. Lachmann
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Reynolds Number ◽  
Wind Tunnel ◽  
Short Distance ◽  
Wind Tunnel Tests ◽  
Theoretical Methods ◽  
Unit Reynolds Number ◽  
Research Department ◽  
Boundary Layer Profile

The method referred to in Dr. Coleman's notes was developed with the collaboration of my colleague Mr. J. B. Edwards of Handley Page Research Department. The purpose was to obtain a rational estimate of suction quantities and suction distribution, linked up with measurements of boundary layer profiles and suction quantities on wind tunnel models, and also to assess the effect of a certain degree of roughness of the order to be expected on actual wings. Existing theoretical methods ignore roughness which, however, is a most important parameter not only in wind tunnel tests, but also in flight at higher values of the unit Reynolds number; surface roughness obviously limits the intensity of suction which can be applied at a spanwise suction strip.It was intuitively assumed that the removal of fluid by suction was equivalent to cutting off the lower portion of the boundary layer profile at the upstream edge of the suction strip and that a rapid re-adjustment of the boundary layer profile within a short distance took place.

Wind effects on rough-walled and smooth-walled large cooling towers

2016 ◽  
Vol 20 (6) ◽  
pp. 843-864 ◽  
Author(s):  
XX Cheng ◽  
L Zhao ◽  
YJ Ge ◽  
R Dong ◽  
C Demartino
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Wind Tunnel ◽  
Flow Field ◽  
Atmospheric Boundary Layer ◽  
Model Test ◽  
Full Scale ◽  
Cooling Towers ◽  
Test Results ◽  
Wind Effects

Adding vertical ribs is recognized as a useful practice for reducing wind effects on cooling towers. However, ribs are rarely used on cooling towers in China since Chinese Codes are insufficient to support the design of rough-walled cooling towers, and an “understanding” hampers the use of ribs, which thinks that increased surface roughness has limited effects on the maximum internal forces that control the structural design. To this end, wind tunnel model tests in both uniform flow field with negligible free-stream turbulence and atmospheric boundary layer (ABL) turbulent flow field are carried out in this article to meticulously study and quantify the surface roughness effects on both static and dynamic wind loads for the purpose of improving Chinese Codes first. Subsequently, a further step is taken to obtain wind effects on a full-scale large cooling tower at a high Re, which are employed to validate the results obtained in the wind tunnel. Finally, the veracity of the model test results is discussed by investigating the Reynolds number (Re) effects on them. It has been proved that the model test results for atmospheric boundary layer flow field are all obtained in the range of Re-independence and the conclusions drawn from model tests and full-scale measurements basically agree, so most model test results presented in this article can be directly applied to the full-scale condition without corrections.

scholarly journals Aerodynamic interference of wind flow around three cylindrical bodies with surface roughness

2020 ◽  
Vol 313 ◽  
pp. 00051
Author(s):  
Michael Macháček ◽  
Shota Urushadze ◽  
Stanislav Pospíšil ◽  
Arsenii Trush ◽  
Miroš Pirner
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Surface Roughness ◽  
Wind Tunnel ◽  
Dynamic Pressure ◽  
Wind Loading ◽  
Wind Flow ◽  
Local Dynamic ◽  
Complex Phenomenon ◽  
Aerodynamic Interference

The aerodynamic interference effect is an important and complex phenomenon that can modified wind flow around structures in a group and wind loading on structures can significantly increase. Three cylindrical buildings in one row with a rough surface and surrounding lower minor buildings were studied by experimental measurement in wind tunnel with a turbulent boundary layer. The experimental study was focused on aerodynamical forces, local dynamic pressure on a facade of the buildings, and visualization of wind flow around buildings.

Modeling and simulation of drag force for coated PET fabric with silica nano particles

2018 ◽  
Vol 30 (3) ◽  
pp. 398-411
Author(s):  
Siamak Nazemi ◽  
Ramin Khajavi ◽  
Hamidreza Rabie Far ◽  
Mohammad Esmail Yazdanshenas ◽  
Manouchehr Raad
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Wind Tunnel ◽  
Drag Force ◽  
Flow Behavior ◽  
Sol Gel ◽  
Boundary Layer Separation ◽  
Nano Particles ◽  
Content Type ◽  
Pet Fabric

Purpose This paper is based on the simulation of wind tunnel experiment for better understanding and predicting the behavior of PET fabric in the wind tunnel. This software calculates the drag force of fabric, illustrates pressure in the surrounding of airfoil and velocity of wind in the tunnel during different angles of attack (0°, 45° and 90°). The paper aims to discuss these issues. Design/methodology/approach The sol-gel method was applied for the synthesis of silica nano particles. So, PET fabric was coated with precursor (Tetra ethyl ortho silicate) solution first and the process continued on PET fabric. The morphology of obtained hydrophobic fabric samples and their surface roughness was observed and determined by atomic microscopes (AFM and SEM). Experimental data were used for simulation and modeling, and then results were interpreted. Findings It was concluded that the surface roughness and its amount can play a significant role in the drag reduction of PET fabric, and surface roughness can change the boundary layer from laminar to turbulent. Originality/value At 45 degrees angle of attack, larger boundary layer separation results in a large increase in the drag force. This model is useful for predicting flow behavior in the experimental wind tunnel.

Prediction of Atmospheric Turbulence Characteristics for Surface Boundary Layer using Empirical Spectral Methods

2020 ◽  
Author(s):  
Yagya Dutta Dwivedi ◽  
Vasishta Bhargava Nukala ◽  
Satya Prasad Maddula ◽  
Kiran Nair
Keyword(s):  
Boundary Layer ◽  
Time Series ◽  
Surface Roughness ◽  
Wind Speed ◽  
Atmospheric Turbulence ◽  
Surface Boundary ◽  
Low Frequencies ◽  
Surface Boundary Layer ◽  
Power Spectral ◽  
Mean Wind Speed

Abstract Atmospheric turbulence is an unsteady phenomenon found in nature and plays significance role in predicting natural events and life prediction of structures. In this work, turbulence in surface boundary layer has been studied through empirical methods. Computer simulation of Von Karman, Kaimal methods were evaluated for different surface roughness and for low (1%), medium (10%) and high (50%) turbulence intensities. Instantaneous values of one minute time series for longitudinal turbulent wind at mean wind speed of 12 m/s using both spectra showed strong correlation in validation trends. Influence of integral length scales on turbulence kinetic energy production at different heights is illustrated. Time series for mean wind speed of 12 m/s with surface roughness value of 0.05 m have shown that variance for longitudinal, lateral and vertical velocity components were different and found to be anisotropic. Wind speed power spectral density from Davenport and Simiu profiles have also been calculated at surface roughness of 0.05 m and compared with k−1 and k−3 slopes for Kolmogorov k−5/3 law in inertial sub-range and k−7 in viscous dissipation range. At high frequencies, logarithmic slope of Kolmogorov −5/3rd law agreed well with Davenport, Harris, Simiu and Solari spectra than at low frequencies.

Boundary layer wind tunnel modeling experiments on pumping ventilation through a three-story reduce-scaled building with two openings

2021 ◽  
pp. 108043
Author(s):  
Huai-Yu Zhong ◽  
Chao Lin ◽  
Yang Sun ◽  
Hideki Kikumoto ◽  
Ryozo Ooka ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel
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