Model-Based Estimation of Mechanical Characters of Arterial Vessels Using Experimental Dynamic Response Data

2011 ◽  
Author(s):  
Rahil Vali ◽  
Takashi Saito
Keyword(s):  
Mechanical Model ◽  
Damping Ratio ◽  
Elastic Shell ◽  
Measurement Data ◽  
Circulatory System ◽  
Stiffness Index ◽  
Working Fluid ◽  
Model Based ◽  
Ring Model ◽  
Downhill Simplex

As both the geometric and stiffness changes may occur in atherosclerosis, it is necessary to estimate respective contribution from structural and material characteristics in the stiffness index. In this study, we employ the primary mechanical model based on one of elastic shell theory, Love’s theory and look upon a blood vessel as a ring model. Furthermore in order to confirm validity of the model, the experiments were carried out on artificial tubes. The circulating circuit is applied as the circulatory system of human body including tubes, and water is designated as the working fluid of the circulating circuit. Experimental data are applied for mechanical model and mechanical parameters are identified using Downhill simplex method as the inverse problem. In this study stiffness index and damping ratio were identified and the result of Love’ theory was compared with measurement data and Donnell’s theory. The result shows that present study can confirm the measurement data with the fine approximation.

Mechanical model based on a BVP for FRPs applied on flat and curved masonry pillars with anchor spikes

2021 ◽  
pp. 114251
Author(s):  
Elisa Bertolesi ◽  
Ernesto Grande ◽  
Mario Fagone ◽  
Gabriele Milani ◽  
Tommaso Rotunno
Keyword(s):  
Mechanical Model ◽  
Model Based

scholarly journals On Damping and Fluidelastic Instability in a Tube Bundle Subjected to Two-Phase Cross-Flow

2007 ◽  
Author(s):  
Joaquin E. Moran ◽  
David S. Weaver
Keyword(s):  
Flow Regime ◽  
Void Fraction ◽  
Tube Bundle ◽  
Damping Ratio ◽  
Pressure Fluctuations ◽  
Cross Flow ◽  
Phase Changes ◽  
Working Fluid ◽  
Two Phase ◽  
Fluidelastic Instability

An experimental study was conducted to investigate damping and fluidelastic instability in tube arrays subjected to two-phase cross-flow. The purpose of this research was to improve our understanding of these phenomena and how they are affected by void fraction and flow regime. The working fluid used was Freon 11, which better models steam-water than air-water mixtures in terms of vapour-liquid mass ratio as well as permitting phase changes due to pressure fluctuations. The damping measurements were obtained by “plucking” the monitored tube from outside the test section using electromagnets. An exponential function was fitted to the tube decay trace, producing consistent damping measurements and minimizing the effect of frequency shifting due to fluid added mass fluctuations. The void fraction was measured using a gamma densitometer, introducing an improvement over the Homogeneous Equilibrium Model (HEM) in terms of density and velocity predictions. It was found that the Capillary number, when combined with the two-phase damping ratio (interfacial damping), shows a well defined behaviour depending on the flow regime. This observation can be used to develop a better methodology to normalize damping results. The fluidelastic results agree with previously presented data when analyzed using the HEM and the half-power bandwidth method. The interfacial velocity is suggested for fluidelastic studies due to its capability for collapsing the fluidelastic data. The interfacial damping was introduced as a tool to include the effects of flow regime into the stability maps.

scholarly journals Proprioception In Insects

1938 ◽  
Vol 15 (1) ◽  
pp. 114-131 ◽  
Author(s):  
J. W. S. PRINGLE
Keyword(s):  
Contact Pressure ◽  
Mode Of Action ◽  
Mechanical Model ◽  
Campaniform Sensilla ◽  
Chemical Substances ◽  
Parallel Orientation ◽  
Model Based ◽  
Vertebrate Limb ◽  
Olfactory Stimuli ◽  
Anatomical Arrangement

1. The campaniform sensilla on the legs of Periplaneta are similar in action to those on the palps, and respond to strains in the cuticle. 2. They are arranged in groups at the joints, with parallel orientation of the sensilla of a group. 3. Tests with various chemical substances show a complete absence of sensitivity to olfactory stimuli. 4. A theory is given of the mode of action of the sensilla in terms of a mechanical model based on their observed structure. Each group of parallel sensilla should act as a unit, responding to those forces which have a compression component of shear in the direction of their long diameters. 5. This theory makes it possible to predict the behaviour of the sensilla from their anatomical arrangement. Most if not all the groups on the legs are so arranged as to be sensitive to the forces present when the insect is standing on the ground. 6. The sensilla probably provide the basis for the sense of contact pressure postulated by Holst (1935), Hoffmann (1933), Crozier & Stier (1928-9), Fraenkel (1932) and others. 7. Comparison of this proprioceptive mechanism with that of the vertebrate limb reveals an absence of qualitative sensitivity that may have an important bearing on the question of the evolution of behaviour.

scholarly journals A Real-Time Dynamic Fuel Cell System Simulation for Model-Based Diagnostics and Control: Validation on Real Driving Data

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3148 ◽  
Author(s):  
Daniel Ritzberger ◽  
Christoph Hametner ◽  
Stefan Jakubek
Keyword(s):  
Fuel Cell ◽  
Real Time ◽  
Combustion Engine ◽  
System Simulation ◽  
Measurement Data ◽  
Fuel Cell Vehicle ◽  
Feedback Controls ◽  
Model Based ◽  
And Control ◽  
Stack Model

Fuel cell systems are regarded as a promising candidate in replacing the internal combustion engine as a renewable and emission free alternative in automotive applications. However, the operation of a fuel cell stack fulfilling transient power-demands poses significant challenges. Efficiency is to be maximized while adhering to critical constraints, avoiding adverse operational conditions (fuel starvation, membrane flooding or drying, etc.) and mitigating degradation as to increase the life-time of the stack. Owing to this complexity, advanced model-based diagnostic and control methods are increasingly investigated. In this work, a real time stack model is presented and its experimental parameterization is discussed. Furthermore, the stack model is integrated in a system simulation, where the compressor dynamics, the feedback controls for the hydrogen injection and back-pressure valve actuation, and the purging strategy are considered. The resulting system simulation, driven by the set-point values of the operating strategy is evaluated and validated on experimental data obtained from a fuel cell vehicle during on-road operation. It will be shown how the internal states of the fuel cell simulation evolve during the transient operation of the fuel cell vehicle. The measurement data, for which this analysis is conducted, stem from a fuel cell research and demonstrator vehicle, developed by a consortium of several academic and industrial partners under the lead of AVL List GmbH.

scholarly journals Damping Measurements in Tube Bundles Subjected to Two-Phase Cross Flow

2006 ◽  
Author(s):  
Joaquin E. Moran ◽  
David S. Weaver
Keyword(s):  
Flow Regime ◽  
Void Fraction ◽  
Mass Flux ◽  
Damping Ratio ◽  
Logarithmic Decrement ◽  
Working Fluid ◽  
Exponential Fitting ◽  
Two Phase ◽  
Tube Bundles ◽  
Half Power

An experimental study was conducted to investigate two-phase damping in tube arrays. The objective was to compare different measurement methodologies in order to obtain a more reliable damping estimate. This will allow for improved guidelines related to failures due to fluidelastic instability in tube bundles. The methods compared were the traditionally used half-power bandwidth, the logarithmic decrement and an exponential fitting to the tube decay response. The working fluid used was Refrigerant 11 (Freon), which better models the real steam-water problem, as it allows for phase change. The void fraction was measured using a gamma densitometer, introducing an improvement over the traditional Homogeneous Equilibrium Model (HEM) in terms of velocity and density predictions. The results obtained by using the half-power bandwidth method agree with data previously reported for two-phase flow. The experiments showed that the half-power bandwidth produces higher damping values than the other two, but only up to a certain void fraction. After that point, the results obtained from the three methods are very similar. The exponential fitting proved to be more consistent than the logarithmic decrement, and it is not as sensitive as the half-power bandwidth to the frequency shifting caused by the change in added mass around the tube. By plotting the damping ratio as a function of void fraction, pitch mass flux and flow regime, we were able to verify that damping is more dependent on void fraction and flow regime than on mass flux.

MEASUREMENT OF FLOW IN CIRCULAR ELASTIC TUBE

2015 ◽  
Vol 76 (10) ◽  
Author(s):  
Muhamad Mazwan Mahat ◽  
Salmiah Kasolang ◽  
Izdihar Tharazi ◽  
R. Nazirul Izzati
Keyword(s):  
Structural Parameters ◽  
Circulatory System ◽  
Elastic Tube ◽  
Tube Length ◽  
Working Fluid ◽  
Circulatory Support ◽  
Pump System ◽  
Initial Work ◽  
Impedance Pump ◽  
Set Up

 Impedance pump is a simple valveless pumping mechanism which typically used in viscosity measurement device to assist pumping of fluid. It is typically connected to an elastic tube in a circulatory system of a more rigid tube. In conventional mechanical circulatory support systems using rotary pump, the pumping mechanism was exposed to turbulent stresses. Hence,  this may cause damage to blood cells flowing through the impeller. There has been initial work on finding alternative solution using the impedance pump system. However,  substantial findings are not yet sufficient to fully understand the mechanism. The purpose of this research is to extend the investigation on impedance pump by specifically looking at the effect of structural parameters on the elastic tube and the flow behaviour. In this study, a closed loop impedance pump system was set up to demonstrate blood flow circulatory system where the mixture of glycerine and water was used as the working fluid. Three variables were regulated namely voltage, tube thickness, and tube length was used in order to get the flowrate of the working fluid. Based on the results, it was found that  tube thickness of 1 mm and a length of 200 mm had produced the highest flowrate in the region 75 ml/min.

scholarly journals Investigation of flow non-uniformities in the cross-flow heat exchanger with elliptical tubes

2019 ◽  
Vol 108 ◽  
pp. 01009 ◽  
Author(s):  
Stanisław Łopata ◽  
Paweł Ocłoń ◽  
Tomasz Stelmach
Keyword(s):  
Heat Exchanger ◽  
Measurement Data ◽  
Cross Flow ◽  
Flow Distribution ◽  
Transitional Flow ◽  
Working Fluid ◽  
Elliptical Cross ◽  
Flow Heat ◽  
The Cross ◽  
Inflow Conditions

In heat exchangers, especially those with the cross-flow arrangement, it is nearly impossible to achieve the uniform distribution of the working fluid in the tubular space with the currently used inlet and outlet chambers (in some constructions as well). The improper inflow conditions to individual tubes, including those with an elliptical cross-section - often used because of their favorable features compared to round tubes, is the cause of improper heat transfer. In this respect, transitional flow is of particular importance. This flow regime is complex and challenging to model. Therefore, it is necessary to perform experimental verification. For this purpose, an appropriate stand was built, allowing to investigate the flow of the working fluid (water) to the elliptical tubes in the cross-current heat exchanger. The paper presents the results of measurements for manifold geometry, which are currently used in practice (for heat exchanger constructions). The analysis of the measurement data confirms the nonuniform flow distribution to individual tubes of the heat exchanger.

Sign in / Sign up

Export Citation Format

Share Document