Modeling of a MEMS Floating Element Shear Sensor

2014 ◽  
Vol 1659 ◽  
pp. 35-42
Author(s):  
Nikolas Kastor ◽  
Zhengxin Zhao ◽  
Robert D. White
Keyword(s):  
Shear Stress ◽  
Laminar Flow ◽  
Pressure Gradient ◽  
Flow Direction ◽  
Flow Cell ◽  
Surface Shear Stress ◽  
Cfd Model ◽  
Shear Sensor ◽  
Floating Element ◽  
Gradient Effects

ABSTRACTA MEMS floating element shear stress sensor has been developed for flow testing applications, targeted primarily in ground and flight testing of aerospace vehicle and components. However, concerns remain about the interaction of the flow with the mechanical elements of the structure at the micro-scale. In particular, there are concerns about the validity of laminar flow cell calibration to measurement in turbulent flows, and the extent to which pressure gradients may introduce errors into the shear stress measurement. In order to address these concerns, a numerical model of the sensor has been constructed.In this paper, a computational fluid dynamics (CFD) model is described. The CFD model directly models a laminar flow cell experiment that is used to calibrate the shear sensor. The computational model allows us to quantify the contributions (e.g. pressure gradient vs. shear, top surface vs. lateral surfaces) to the sensor output in a manner that is difficult by purely experimental means. The results are compared to experimental data, validating the model and resulting in the following: Surface shear stress contributes approximately 40% of the total flow direction force; pressure gradient effects contribute nearly 45% for the textured shuttle described here; lift forces and pitching moments are non-zero. Thus, it is found that flow interactions are complex and that it is insufficient to simply assume that flow forces on the sensor are the top area multiplied by wall shear, as is sometimes done. Pressure gradient effects, at least, must be included for accurate calibration.

Development of a floating element for the measurement of surface shear stress

AIAA Journal ◽  
1985 ◽  
Vol 23 (3) ◽  
pp. 410-415 ◽  
Author(s):  
M. Acharya ◽  
J. Bornstein ◽  
M. P. Escudier ◽  
V. Vokurka
Keyword(s):  
Shear Stress ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Floating Element

LES of turbulent surface shear stress and pressure-gradient-driven flow on shallow continental shelves

2011 ◽  
Vol 61 (9) ◽  
pp. 1369-1390 ◽  
Author(s):  
Guillaume Martinat ◽  
Ying Xu ◽  
Chester E. Grosch ◽  
Andrés E. Tejada-Martínez
Keyword(s):  
Shear Stress ◽  
Pressure Gradient ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Continental Shelves

An Analysis of Jet Stripping of Liquid Coatings

1984 ◽  
Vol 106 (4) ◽  
pp. 399-404 ◽  
Author(s):  
C. H. Ellen ◽  
C. V. Tu
Keyword(s):  
Shear Stress ◽  
Pressure Gradient ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Gradient Effect ◽  
Theoretical Predictions ◽  
Coating Mass ◽  
Stress Term ◽  
Good Agreement

This paper presents a new analysis of the jet stripping process, as used to control coating thicknesses in the paper, photographic and galvanizing industries, and demonstrates that the inclusion of a surface shear stress term, acting in conjunction with the pressure gradient on the coating, gives theoretical predictions of coating behavior quite different from those based on stripping which allows only for pressure gradient effect. An illustration is given of how jets operating close to, and further from, the strip during hot dip galvanizing have different effects on the molten coating even though the final coating mass might be the same. Measurements of coating mass, taken from galvanizing line trials, have shown good agreement with the revised theory.

scholarly journals The Calibration of a Surface Mounted Aerodynamic Wall Shear Stress Gauge in Laminar Flow With a Free-Stream Pressure Gradient

1995 ◽  
Author(s):  
James T. Duffy ◽  
Mark R. D. Davies ◽  
Leona Hamilton
Keyword(s):  
Shear Stress ◽  
Laminar Flow ◽  
Wall Shear Stress ◽  
Pressure Gradient ◽  
Cross Flow ◽  
Calibration Method ◽  
Cylindrical Shape ◽  
Suction Surface ◽  
Wall Shear ◽  
Semi Empirical

A method of calibrating surface mounted thin film gauges to measure aerodynamic wall shear stress in laminar flow is presented. Hot wire measurements from the boundary-layer on a flat plate are used to find the first calibration constant and the shear stress predictions for a cylinder in cross flow are used to find the second. The cylindrical shape incorporates a favourable pressure gradient into the calibration method. Good agreement has been found between aerodynamic experimental results for the two shapes which suggests that a unique calibration exists. All experiments used Dantec 55R47 gauges operated at an overheat of 383 K above a reference temperature of 293 K. A new semi-empirical theory is used for the purpose of calibration. Input of experimental data enables the calculation of the equation parameters so that the new theory may be applied to a gauge mounted on a variety of surface profiles. Finally, calibrated gauges are used to measure the wall shear stress in laminar flow at four chordwise positions on the suction surface of a turbine blade in a two dimensional cascade.

scholarly journals Significance of Slippage and Electric Field in Mucociliary Transport of Biomagnetic Fluid

Lubricants ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 48
Author(s):  
Sufian Munawar
Keyword(s):  
Shear Stress ◽  
Flow Direction ◽  
Pressure Rise ◽  
Physical Parameters ◽  
Slippage Effect ◽  
Channel Surface ◽  
Electro Osmosis ◽  
Biomagnetic Fluid ◽  
Velocity Pressure ◽  
Metachronal Waves

Shear stress at the cilia wall is considered as an imperative factor that affects the efficiency of cilia beatings as it describes the momentum transfer between the fluid and the cilia. We consider a visco-inelastic Prandtl fluid in a ciliated channel under electro-osmotic pumping and the slippage effect at cilia surface. Cilia beating is responsible for the stimulation of the flow in the channel. Evenly distributed cilia tend to move in a coordinated rhythm to mobilize propulsive metachronal waves along the channel surface by achieving elliptic trajectory movements in the flow direction. After using lubrication approximations, the governing equations are solved by the perturbation method. The pressure rise per metachronal wavelength is obtained by numerically integrating the expression. The effects of the physical parameters of interest on various flow quantities, such as velocity, pressure gradient, pressure rise, stream function, and shear stress at the ciliated wall, are discussed through graphs. The analysis reveals that the axial velocity is enhanced by escalating the Helmholtz–Smoluchowski velocity and the electro-osmosis effects near the elastic wall. The shear stress at the ciliated boundary elevates with an increase in the cilia length and the eccentricity of the cilia structure.

Visualization of separation and reattachment in an incident shock-induced interaction

2021 ◽  
pp. 095441002098349
Author(s):  
Yun Jiao ◽  
Chengpeng Wang
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
Shear Stress ◽  
Separation Bubble ◽  
Incident Shock ◽  
Incident Shock Wave ◽  
Bottom Wall ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Oil Flow

An experimental study is conducted on the qualitative visualization of the flow field in separation and reattachment flows induced by an incident shock interaction by several techniques including shear-sensitive liquid crystal coating (SSLCC), oil flow, schlieren, and numerical simulation. The incident shock wave is generated by a wedge in a Mach 2.7 duct flow, where the strength of the interaction is varied from weak to moderate by changing the angle of attack α of the wedge from 8° and 10° to 12°. The stagnation pressure upstream was set to approximately 607.9 kPa. The SSLCC technique was used to visualize the surface flow characteristics and analyze the surface shear stress fields induced by the initial incident shock wave over the bottom wall and sidewall experimentally which resolution is 3500 × 200 pixels, and the numerical simulation was also performed as the supplement for a clearer understanding to the flow field. As a result, surface shear stress over the bottom wall was visualized qualitatively by SSLCC images, and flow features such as separation/reattachment and the variations of position/size of separation bubble with wedge angle were successfully distinguished. Furthermore, analysis of shear stress trend over the bottom wall by a hue value curve indicated that the relative magnitude of shear stress increased significantly downstream of the separation bubble compared with that upstream. The variation trend of shear stress was consistent with the numerical simulation results, and the error of separation position was less than 2 mm. Finally, the three-dimensional schematic of incident shock-induced interaction has been achieved by qualitative summary by multiple techniques, including SSLCC, oil flow, schlieren, and numerical simulation.

Exploring wall shear stress spatiotemporal heterogeneity in coronary arteries combining correlation-based analysis and complex networks with computational hemodynamics

2020 ◽  
Vol 234 (11) ◽  
pp. 1209-1222 ◽  
Author(s):  
Karol Calò ◽  
Giuseppe De Nisco ◽  
Diego Gallo ◽  
Claudio Chiastra ◽  
Ayla Hoogendoorn ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Complex Networks ◽  
Coronary Arteries ◽  
Early Stage ◽  
Flow Direction ◽  
Computational Hemodynamics ◽  
Time Histories ◽  
Wall Shear

Atherosclerosis at the early stage in coronary arteries has been associated with low cycle-average wall shear stress magnitude. However, parallel to the identification of an established active role for low wall shear stress in the onset/progression of the atherosclerotic disease, a weak association between lesions localization and low/oscillatory wall shear stress has been observed. In the attempt to fully identify the wall shear stress phenotype triggering early atherosclerosis in coronary arteries, this exploratory study aims at enriching the characterization of wall shear stress emerging features combining correlation-based analysis and complex networks theory with computational hemodynamics. The final goal is the characterization of the spatiotemporal and topological heterogeneity of wall shear stress waveforms along the cardiac cycle. In detail, here time-histories of wall shear stress magnitude and wall shear stress projection along the main flow direction and orthogonal to it (a measure of wall shear stress multidirectionality) are analyzed in a representative dataset of 10 left anterior descending pig coronary artery computational hemodynamics models. Among the main findings, we report that the proposed analysis quantitatively demonstrates that the model-specific inlet flow-rate shapes wall shear stress time-histories. Moreover, it emerges that a combined effect of low wall shear stress magnitude and of the shape of the wall shear stress–based descriptors time-histories could trigger atherosclerosis at its earliest stage. The findings of this work suggest for new experiments to provide a clearer determination of the wall shear stress phenotype which is at the basis of the so-called arterial hemodynamic risk hypothesis in coronary arteries.

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