Frequency response analysis of guard-heated hot-film wall shear stress sensors for turbulent flows

2014 ◽  
Vol 46 ◽  
pp. 61-69 ◽  
Author(s):  
Ali Etrati ◽  
Rustom B. Bhiladvala
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Frequency Response ◽  
Turbulent Flows ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
Stress Sensors ◽  
Shear Stress Sensors ◽  
Wall Shear Stress Sensors ◽  
Hot Film

High Performance SOI-CMOS Wall Shear Stress Sensors

2007 ◽  
Author(s):  
Ibraheem Haneef ◽  
Syed Zeeshan Ali ◽  
Florin Udrea ◽  
John D. Coull ◽  
Howard P. Hodson
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
High Performance ◽  
Stress Sensors ◽  
Shear Stress Sensors ◽  
Wall Shear ◽  
Wall Shear Stress Sensors ◽  
Soi Cmos

scholarly journals The Effect of Sensor Dimensions on the Performance of Flexible Hot Film Shear Stress Sensors

Micromachines ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 305 ◽  
Author(s):  
Jin-Jin Wang ◽  
Hong Hu ◽  
Chao-Zhan Chen
Keyword(s):  
Shear Stress ◽  
Frequency Response ◽  
Flexible Substrate ◽  
Substrate Material ◽  
Film Sensor ◽  
Stress Sensors ◽  
Shear Stress Sensors ◽  
Length Width ◽  
Hot Film ◽  
Hot Film Sensor

This paper presents a study to determine the effect of sensor dimensions (length, width, and thickness) on the performance of flexible hot film shear stress sensors. The sensing component of a hot film sensor is nickel thermistor, and the flexible substrate material is polyimide. Several groups of flexible hot film shear stress sensors with different lengths, widths, and thicknesses were studied. The temperature coefficient of resistance (TCR) was measured. The TCR increased slightly with increasing thickness. The frequency response (time constant) of the flexible hot film shear stress sensor was obtained by the square wave, while the sensitivity was tested in a wind tunnel. The study found that as the sensor length was shortened, the frequency response increased, and the sensitivity decreased.

Design and Analysis of a Shear Stress Sensor for Microcirculation Investigations (Invited Paper)

2003 ◽  
Author(s):  
Risa Robinson ◽  
Lynn Fuller ◽  
Harvey Palmer ◽  
Mary Frame
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Computational Technique ◽  
Flow Modification ◽  
Stress Sensors ◽  
Shear Stress Sensors ◽  
Wall Shear

Blood flow regulation in the microvascular network has been investigated by means of computational fluid dynamics, in vivo particle tracking and microchannel models. It is evident from these studies that shear stress along the wall is a key factor in the communication network that results in blood flow modification, yet current methods for shear stress determination are acknowledged to be imprecise. Micromachining technology allows for the development of implantable shear stress sensors that will enable us to monitor wall shear stress at multiple locations in arteriole bifurcations. In this study, a microchannel was employed as an in vitro model of a microvessel. Thermal shear stress sensors were used to mimic the endothelial cells that line the vessel wall. A three dimensional computational model was created to simulate the system’s thermal response to the constant temperature control circuit and related wall shear stress. The model geometry included a silicon wafer section with all the fabrication layers — silicon dioxide, poly silicon resistor, silicon nitride — and a microchannel with cross section 17 μm × 17 μm. This computational technique was used to optimize the dimensions of the system for a 0.01 Reynolds number flow at room temperature in order to reduce the amount of heat lost to the substrate and to predict and maximize the signal response. Results of the design optimization are presented and the fabrication process discussed.

A Technique for the Measurement of Wall Shear Stress Based on Micro Fabricated Hot-Film Sensor

2013 ◽  
Author(s):  
Takuya Sawada ◽  
Osamu Terashima ◽  
Yasuhiko Sakai ◽  
Kouji Nagata ◽  
Mitsuhiro Shikida ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Flows ◽  
Temporal Resolution ◽  
Large Scale ◽  
High Temporal Resolution ◽  
Film Sensor ◽  
Wall Shear ◽  
Hot Film ◽  
Hot Film Sensor

The objective of this study is to establish a technique for accurately measuring the wall shear stress in turbulent flows using a micro-fabricated hot-film sensor. Previously, we developed a hot-film sensor with a flexible polyimide-film substrate. This sensor can be attached to curved walls and be used in various situations. Furthermore, the sensor has a 20-μm-wide, heated thin metal film. However, the temporal resolution of this hot-film sensor is not very high owing to its substrate’s high heat capacity. Consequently, its performance is inadequate for measuring the wall shear stress “fluctuations” in turbulent flows. Therefore, we have developed another type of hot-film sensor in which the substrate is replaced with silicon, and a cavity has been introduced under the hot-film for reducing heat loss from the sensor and achieving high temporal resolution. Furthermore, for improving the sensor’s spatial resolution, the width of the hot-film is decreased to 10 μm. The structure of the hot-film’s pattern and the flow-detection mechanism are similar to those of the previous sensor. Experimental results show that new hot-film sensor works as expected and has better temporal resolution than the previous hot-film sensor. As future work, we will measure the wall shear stress for a turbulent wall-jet and discuss the relationship between a large-scale coherent vortex structure and wall shear stress based on data obtained using the new hot-film sensor.

Can We Rescue Thermal Wall Shear Stress Sensing?

2011 ◽  
Author(s):  
Elsa Assadian ◽  
Rustom B. Bhiladvala
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Turbulent Flows ◽  
Working Fluid ◽  
Single Element ◽  
Film Sensor ◽  
Wall Shear ◽  
Stress Sensing ◽  
Heater Length ◽  
Hot Film

The use of single flush-mounted thin-films for thermal sensing of wall shear stress fluctuations in turbulent flows has seen a decline, in spite of their non-intrusiveness, and the availability of microfabrication technologies to create very small films. The limitations of such single-element sensors are quite severe—their spatial resolution is not determined by their size alone, but modified by substrate heat conduction which creates variations in the effective sensor size (heat exchange area), dependent on strength and timescale of the fluctuations. Here a two-element design is investigated—with the hot-film sensor element surrounded by an electrically isolated guard heater film maintained at the same temperature as the sensor, but controlled by a separate anemometer circuit. Numerical studies are used to examine such guard heater designs over a range of shear stress values. The results show that if the sensor film center-location is biased towards the downstream end (75% and 65% of guard-heater length for water and air, respectively), with an appropriately-sized guard heater, 95% of the total heat generated in the sensing film can be transferred directly to the fluid, for strong turbulent fluctuations (Peclet number Pe > 8000) when the working fluid is water.

Sign in / Sign up

Export Citation Format

Share Document