scholarly journals Sensitivity Investigation on the Pressure Coefficients Non-Dimensionalization

2021 ◽  
Vol 6 (4) ◽  
pp. 53
Author(s):  
Fabio Rizzo
Keyword(s):  
Wind Tunnel ◽  
Wind Velocity ◽  
Time History ◽  
Wind Tunnels ◽  
Pressure Coefficients ◽  
Box Section ◽  
Large Structures ◽  
Suspended Bridge

The scaling of large structures to investigate their aerodynamics in wind tunnels is a common and robust procedure to estimate important magnitudes, including pressure coefficients. Different aspects can affect the estimation of pressure coefficients; four examples are the non-dimensionalization, blockage, non-stationarity, and non-Gaussianity of the wind tunnel velocity. This paper shows the variability of pressure coefficients due to these four aspects for the case study of a closed box section of a suspended bridge. It was estimated that the pressure coefficients of similar pressure taps vary significantly due to different sets of wind velocity time history used to non-dimensionalize the wind tunnel pressures. In addition, the stationarity of the wind velocity process was not confirmed for all wind velocity sets and the non-Gaussianity of the wind velocity time history was confirmed.

Blockage Corrections for Rectangular Flat Plates Mounted in an Open Jet Wind Tunnel

1983 ◽  
Vol 197 (4) ◽  
pp. 259-263 ◽  
Author(s):  
A T Sayers ◽  
D R Ball
Keyword(s):  
Wind Tunnel ◽  
Flat Plate ◽  
Wind Velocity ◽  
Experimental Technique ◽  
Flow Direction ◽  
The Body ◽  
Wind Tunnels ◽  
Flat Plates ◽  
Projected Area

The correction that must be applied to the upstream wind velocity, when a rectangular flat plate normal to the flow direction is placed in an open jet wind tunnel, is determined and is found to be at all times equal to or greater than unity. It is also found to be dependent upon the distance of the body from the tunnel outlet, and the projected area of the body. Comparisons with previous work carried out in closed wind tunnels are made to confirm the experimental technique used.

Comparison Research on Aerodynamic Drags and Pressure Coefficients of Reference Car Models in Automotive Wind Tunnel

2014 ◽  
Vol 989-994 ◽  
pp. 2834-2838 ◽  
Author(s):  
Ying Chao Zhang ◽  
Wei Ding ◽  
Zhe Zhang ◽  
Jie Li
Keyword(s):  
Wind Tunnel ◽  
Test Data ◽  
Wind Tunnels ◽  
Actual Situation ◽  
Wind Tunnel Tests ◽  
Reliable Test ◽  
Pressure Coefficients ◽  
Reference Models ◽  
Comparison Research ◽  
Research Show

The aerodynamic drags of different reference car models were investigated to calibrate the performance of the Automotive Wind Tunnel in Jilin University. The two kinds of reference models--MIRA and SAE reference car models were involved in this paper, considering the actual situation of the Automotive Wind Tunnel in Jilin University. The results of the research show that the Automotive Wind Tunnel in Jilin University can meet the demand for automotive wind tunnel tests and it can get the same performances as other wind tunnels have and reliable test data can be obtained in it.

A numerical approach for the assessment of crosswind effects on barrier-protected trains running on bridges

2021 ◽  
Author(s):  
Giuseppe Porpiglia ◽  
Paolo Schito ◽  
Tommaso Argentini ◽  
Alberto Zasso
Keyword(s):  
Wind Tunnel ◽  
Velocity Profile ◽  
Wind Velocity ◽  
Aerodynamic Force ◽  
Numerical Approach ◽  
Aerodynamic Performance ◽  
Vehicle Speed ◽  
Initial Condition ◽  
Cfd Analyses ◽  
Moving Train

<p>This paper introduces a new methodology to assess the influence of a windscreen on the crosswind performance of trains running on a bridge. Considering the difficulties encountered in both carrying out wind tunnel tests that consider the vehicle speed or complete CFD analyses, a simplified CFD approach is here discussed. Instead of simulating simultaneously the windscreen plus the moving train, the numerical problem is split into two parts: firstly, a simulation of the windshield alone is used to extract the perturbed velocity profile at the railway location; secondly, this profile used as an inlet condition for the wind velocity acting on an isolated train. The method is validated against a complete train plus windshield simulation in terms of pressure distribution and aerodynamic force coefficients on the train, and flow streamlines. This approach opens to the possibility of evaluating the aerodynamic performance of a vehicle on bridges considering bridge and vehicle as separated. Wind velocity profiles measured on the bridge during a wind tunnel campaign could be used as the initial condition for numerical simulations on vehicles.</p>

Model Test Techniques Developed to Investigate the Wind Heeling Characteristics of Sailing Vessels and Their Response to Gusts

1991 ◽  
Author(s):  
Barry Deakin
Keyword(s):  
Wind Tunnel ◽  
Model Test ◽  
Wind Tunnels ◽  
Stability Assessment ◽  
Tunnel Floor ◽  
The Stability ◽  
Scaled Models ◽  
Scale Data ◽  
Heeling Moment ◽  
Gust Response

During the development of new stability regulations for the U.K. Department of Transport, doubt was cast over many of the assumptions made when assessing the stability of sailing vessels. In order to investigate the traditional methods a programme of work was undertaken including wind tunnel tests and full scale data acquisition. The work resulted in a much improved understanding of the behaviour of sailing vessels and indeed indicated that the conventional methods of stability assessment are invalid, the rules now applied in the U.K. being very different to those in use elsewhere. The paper concentrates on the model test techniques which were developed specifically for this project but which will have implications to other vessel types. The tests were of two kinds: measurement of the wind forces and moments on a sailing vessel; and investigation of the response of sailing vessels to gusts of wind. For the force and moment measurements models were mounted in a tank of water on a six component balance and tested in a large boundary layer wind tunnel. Previous tests in wind tunnels have always concentrated on performance and the heeling moments have not normally been measured correctly. As the measurements of heeling moment at a range of heel angles was of prime importance a new balance and mounting system was developed which enabled the above water part of the vessel to be modelled correctly, the underwater part to be unaffected by the wind, and the interface to be correctly represented without interference. Various effects were investigated including rig type, sheeting, heading, heel angle and wind gradient. The gust response tests were conducted with Froude scaled models floating in a pond set in the wind tunnel floor. A mechanism was installed in the tunnel which enabled gusts of various characteristics to be generated, and the roll response of the models was measured with a gyroscope. These tests provided information on the effects of inertia, damping, rolling and the characteristics of the gust. Sample results are presented to illustrate the uses to which these techniques have been put.

A Theoretical Investigation of the Maximum-lift Coefficient

1935 ◽  
Vol 39 (295) ◽  
pp. 619-632
Author(s):  
TH. Von karman ◽  
Clark B. Millikan
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Wind Tunnel ◽  
Theoretical Investigation ◽  
Lift Coefficient ◽  
Wind Tunnels ◽  
California Institute ◽  
California Institute Of Technology ◽  
Junior Author ◽  
Institute Of Technology

The problem of the maximum lift of airfoils has concerned the authors greatly since there were first discovered in the spring of 1932 serious discrepancies in this characteristic between results obtained in the wind tunnel of the Guggenheim Aeronautics Laboratory at the California Institute of Technology (GALCIT) and those reported from certain other wind tunnels. An elaborate experimental investigation by the junior author and A. L. Klein indicated that the value of CLmax for a given airfoil was strongly affected both by Reynolds number and by the degree of turbulence in the tunnel wind stream.

scholarly journals Experimental Investigation of a Prandtl Probe Fabricated Using Desktop Stereolithography Technology

2020 ◽  
Vol 5 (10) ◽  
pp. 1274-1280
Author(s):  
Alfred Gift Mwachugha ◽  
Jean Byiringiro ◽  
Harrison Ngetha ◽  
Thomas Carolus ◽  
Kathrin Stahl
Keyword(s):  
Additive Manufacturing ◽  
Wind Tunnel ◽  
Accurate Determination ◽  
Wind Tunnels ◽  
Research Institution ◽  
Flow Characterization ◽  
Desktop Manufacturing ◽  
Flow Quality ◽  
Manufacturing Platform

A Prandtl probe is one of the standard instruments used for flow characterization in wind tunnel facilities. The convectional fabrication method of this instrument requires skilled artisanship, precision drilling, lathing and soldering of its several parts. This reflects into high costs of production in turn making wind energy studies expensive. With the adoption of additive manufacturing, the tooling costs, skills required and design to manufacture constraints can be addressed. This research presents a Prandtl probe that was designed using NX™ software, fabricated by desktop stereolithography additive manufacturing platform and validated in a wind tunnel for velocity range of 0 m/s to 51 m/s. This research attested the option of fabricating relatively cheap functional Prandtl probe with desktop stereolithography technology which can be used for accurate determination of flow quality in wind tunnels experiments. This provides various learning and research institution in developing countries that have already invested in additive desktop manufacturing technology certainty and a cheaper option to fabricate wind research instruments for use at their laboratories. Moreover, fabrication and validation of a 5-hole Prandtl probe can also be examined.

scholarly journals The Problem of Airflow Around Building Clusters in Different Configurations

2017 ◽  
Vol 64 (3) ◽  
pp. 401-418 ◽  
Author(s):  
Mateusz Jędrzejewski ◽  
Marta Poćwierz ◽  
Katarzyna Zielonko-Jung
Keyword(s):  
Numerical Simulation ◽  
Wind Tunnel ◽  
Pressure Measurement ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Complex Model ◽  
Stress Model ◽  
Qualitative Information ◽  
Pressure Coefficients ◽  
Rsm Model

Abstract In the paper, the authors discuss the construction of a model of an exemplary urban layout. Numerical simulation has been performed by means of a commercial software Fluent using two different turbulence models: the popular k-ε realizable one, and the Reynolds Stress Model (RSM), which is still being developed. The former is a 2-equations model, while the latter – is a RSM model – that consists of 7 equations. The studies have shown that, in this specific case, a more complex model of turbulence is not necessary. The results obtained with this model are not more accurate than the ones obtained using the RKE model. The model, scale 1:400, was tested in a wind tunnel. The pressure measurement near buildings, oil visualization and scour technique were undertaken and described accordingly. Measurements gave the quantitative and qualitative information describing the nature of the flow. Finally, the data were compared with the results of the experiments performed. The pressure coefficients resulting from the experiment were compared with the coefficients obtained from the numerical simulation. At the same time velocity maps and streamlines obtained from the calculations were combined with the results of the oil visualisation and scour technique.

scholarly journals Spectral analysis of multiple cracked beam subjected to moving load

2014 ◽  
Vol 36 (4) ◽  
pp. 245-254
Author(s):  
N. T. Khiem ◽  
P. T. Hang
Keyword(s):  
Dynamic Response ◽  
Moving Load ◽  
Time History ◽  
Theoretical Development ◽  
Multiple Cracks ◽  
Spectral Approach ◽  
Cracked Beam ◽  
Time History Response ◽  
Numerical Case Study

In present paper, the spectral approach is proposed for analysis of multiple cracked beam subjected to general moving load that allows us to obtain explicitly dynamic response of the beam in frequency domain. The obtained frequency response is straightforward to calculate time history response by using the FFT algorithm and provides a novel tool to investigate effect of position and depth of multiple cracks on the dynamic response. The analysis is important to develop the spectral method for identification of multiple cracked beam by using its response to moving load. The theoretical development is illustrated and validated by numerical case study.

scholarly journals Variation of diurnal Turbulence Kinetic Energy using sonic anemometer observation: a case study Ledeng, Bandung

2018 ◽  
Author(s):  
Sandy Hardian Susanto Herho ◽  
Dasapta Erwin Irawan
Keyword(s):  
Kinetic Energy ◽  
Diurnal Variation ◽  
Wind Velocity ◽  
Sonic Anemometer ◽  
Diurnal Variations ◽  
Turbulence Kinetic Energy ◽  
Atmospheric Conditions

Sonic anemometer observation was performed on 29 - 30 September 2014 in Ledeng, Bandung to see diurnal variations of Turbulence Kinetic Energy (TKE) that occurred in this area. The measured sonic anemometer was the wind velocity components u, v, and w. From the observation result, it can be seen that the diurnal variation that happened was quite significant. The maximum TKE occurs during the daytime when atmospheric conditions tend to be unstable. TKE values were small at night when atmospheric conditions are more stable than during the daytime.

scholarly journals Measurement of Acceleration Response Functions with Scalable Low-Cost Devices. An Application to the Experimental Modal Analysis

Sensors ◽  
2021 ◽  
Vol 21 (19) ◽  
pp. 6637
Author(s):  
Alvaro Magdaleno ◽  
Juan Villacorta ◽  
Lara del-Val ◽  
Alberto Izquierdo ◽  
Antolin Lorenzana
Keyword(s):  
Modal Analysis ◽  
Lower Cost ◽  
Low Cost ◽  
Micro Electro Mechanical System ◽  
Response Functions ◽  
Large Structures ◽  
Frequency Domains ◽  
Recorded Data ◽  
Applied Forces

One of the most popular options in the Structural Health Monitoring field is the tracking of the modal parameters, which are estimated through the frequency response functions of the structure, usually in the form of accelerances, which are computed as the ratio between the measured accelerations and the applied forces. This requires the use of devices capable of synchronously recording accelerations at several points of the structure at high sampling rates and the subsequent computational analysis using the recorded data. To this end, this work presents and validates a new scalable acquisition system based on multiple myRIO devices and digital MEMS (Micro-Electro-Mechanical System) accelerometers, intended for modal analysis of large structures. A simple form of this system was presented by the authors in a previous work, showing that a single board with some accelerometers connected to it got to obtain high quality measurements in both time and frequency domains. Now, a larger system composed by several slave boards connected and synchronized to a master one is presented. Delays lower than 100 ns are found between the synchronised channels of the proposed system. For validation purposes, a case study is presented where the devices are deployed on a timber platform to estimate its modal properties, which are compared with the ones provided by a commercial system, based on analog accelerometers, to show that similar results are obtained at a significantly lower cost.

Sign in / Sign up

Export Citation Format

Share Document