Analysis of an Artificial Ventricle and Mock Circulatory System

1977 ◽  
Vol 99 (4) ◽  
pp. 184-188 ◽  
Author(s):  
K. M. High ◽  
J. A. Brighton ◽  
A. D. Brickman ◽  
W. S. Pierce
Keyword(s):  
Artificial Heart ◽  
Circulatory System ◽  
Experimental Tests ◽  
Mean Flow ◽  
Actual System ◽  
Mock Circulatory System ◽  
System A ◽  
The Mean ◽  
Artificial Ventricle ◽  
Good Agreement

A mathematical model is developed for calculating the pressures and flows in an artificial heart, its pneumatic drive unit, and a mock circulatory system. The system is divided into convenient subsystems to facilitate the analysis, and each subsystem is then analyzed separately. The set of independent equations developed is solved on a computer and corresponding experimental tests are made on the actual system. A comparison of the experimental and computer results shows good agreement for the mean flow rate through the pump and also for several instantaneous pressures and flow rates in the system.

Use of a Catecholamine Sensor in the Control of an Artificial Heart System

1997 ◽  
Vol 20 (1) ◽  
pp. 37-42 ◽  
Author(s):  
K. Mabuchi ◽  
T. Chinzei ◽  
Y. Abe ◽  
K. Imanishi ◽  
T. Isoyama ◽  
...  
Keyword(s):  
Control System ◽  
Plasma Proteins ◽  
Artificial Heart ◽  
Circulatory System ◽  
Reference Electrode ◽  
Mock Circulatory System ◽  
Real Time Measurement ◽  
Artificial Hearts ◽  
Set Up ◽  
Catecholamine Concentration

An electrochemical sensor system to allow real-time measurement and feedback of catecholamine concentrations was developed for use in the control of artificial hearts. Electrochemical analyses were carried out using a carbon fiber working electrode, an Ag-AgCI reference electrode, and a potentiostat. The operating parameters of the pneumatically-driven artificial heart system were altered in accordance with the algorithm for changes in the catecholamine concentration. The minimum detectable concentrations of both adrenaline and noradrenaline in a mock circulatory system using a phosphate-buffered solution were approximately 1-2 ng/ml (10-8 mol/L). An artificial heart control system utilizing this set-up performed satisfactorily without delay, although sensor sensitivity decreased when placed in goat plasma instead of a phosphate-buffered solution, due to the adsorption of various substances such as plasma proteins onto the electrodes. This study demonstrated the future feasibility of a feedback control system for artificial hearts using catecholamine concentrations.

Application of Various Combustion Models to a Generic Combustor

2003 ◽  
Author(s):  
Lei-Yong Jiang ◽  
Ian Campbell
Keyword(s):  
Experimental Tests ◽  
Combustion Model ◽  
Discrete Ordinates ◽  
Experimental Measurements ◽  
Finite Rate ◽  
Zone Length ◽  
Combustion Models ◽  
The Mean ◽  
Heat Transfers ◽  
Good Agreement

The flow-field of a generic gas combustor with interior and exterior conjugate heat transfers was numerically studied. Results obtained from three combustion models, combined with the re-normalization group (RNG) k-ε turbulence model, discrete ordinates radiation model, and partial equilibrium NOx model are presented and discussed. The numerical results are compared with a comprehensive database obtained from a series of experimental tests. The flow patterns and the recirculation zone length are excellently predicted, and the mean axial velocities are in fairly good agreement with the experimental measurements, particularly at downstream sections for all three combustion models. The mean temperature profiles are also fairly well captured by the probability density function (PDF) and eddy dissipation (EDS) combustion models. The EDS-finite-rate combustion model fails to provide acceptable temperature field. In general, the PDF shows some superiority over the EDS and EDS-finite-rate models. NOx levels predicted by the EDS model are in reasonable agreement with the experimental measurements.

A Continuous Prediction Method for Fully Developed Laminar, Transitional, and Turbulent Flows in Pipes

1975 ◽  
Vol 42 (1) ◽  
pp. 51-54 ◽  
Author(s):  
N. W. Wilson ◽  
R. S. Azad
Keyword(s):  
Turbulent Flows ◽  
Flow Characteristics ◽  
Prediction Method ◽  
Reynolds Numbers ◽  
Mean Flow ◽  
Number Range ◽  
Circular Pipes ◽  
The Mean ◽  
Single Set ◽  
Good Agreement

A single set of equations is developed to predict the mean flow characteristics in long circular pipes operating at laminar, transitional, and turbulent Reynolds numbers. Generally good agreement is obtained with available data in the Reynolds number range 100 < Re < 500,000.

The dispersion of matter in turbulent flow through a pipe

1954 ◽  
Vol 223 (1155) ◽  
pp. 446-468 ◽  
Keyword(s):  
Turbulent Flow ◽  
Capillary Tube ◽  
Resistance Coefficient ◽  
Mean Flow ◽  
Combined Action ◽  
Flow Through ◽  
The Mean ◽  
Coefficient Of Diffusion ◽  
Good Agreement ◽  
Made In

The dispersion of soluble matter introduced into a slow stream of solvent in a capillary tube can be described by means of a virtual coefficient of diffusion (Taylor 1953 a ) which represents the combined action of variation of velocity over the cross-section of the tube and molecluar diffusion in a radial direction. The analogous problem of dispersion in turbulent flow can be solved in the same way. In that case the virtual coefficient of diffusion K is found to be 10∙1 av * or K = 7∙14 aU √ γ . Here a is the radius of the pipe, U is the mean flow velocity, γ is the resistance coefficient and v * ‘friction velocity’. Experiments are described in which brine was injected into a straight 3/8 in. pipe and the conductivity recorded at a point downstream. The theoretical prediction was verified with both smooth and very rough pipes. A small amount of curvature was found to increase the dispersion greatly. When a fluid is forced into a pipe already full of another fluid with which it can mix, the interface spreads through a length S as it passes down the pipe. When the interface has moved through a distance X , theory leads to the formula S 2 = 437 aX ( v * / U ). Good agreement is found when this prediction is compared with experiments made in long pipe lines in America.

Validation of Cardiac Output as Reported by a Permanently Implanted Wireless Sensor

2015 ◽  
Vol 10 (1) ◽  
Author(s):  
Michael Tree ◽  
Jason White ◽  
Prem Midha ◽  
Samantha Kiblinger ◽  
Ajit Yoganathan
Keyword(s):  
Heart Failure ◽  
Cardiac Output ◽  
Measurement Accuracy ◽  
Circulatory System ◽  
Left Heart Failure ◽  
Mock Circulatory System ◽  
System A ◽  
Reference Flow ◽  
Relevant Range

The CardioMEMS heart failure (HF) system was tested for cardiac output (CO) measurement accuracy using an in vitro mock circulatory system. A software algorithm calculates CO based on analysis of the pressure waveform as measured from the pulmonary artery, where the CardioMEMS system resides. Calculated CO was compared to that from reference flow probe in the circulatory system model. CO measurements were compared over a clinically relevant range of stroke volumes and heart rates with normal, pulmonary hypertension (PH), decompensated left heart failure (DLHF), and combined DHLF + PH hemodynamic conditions. The CardioMEMS CO exhibited minimal fixed and proportional bias.

Dynamic Model of a Sac-Type Pneumatically Driven Artificial Ventricle

1977 ◽  
Vol 99 (1) ◽  
pp. 14-19 ◽  
Author(s):  
D. B. Geselowitz ◽  
G. E. Miller ◽  
W. M. Phillips
Keyword(s):  
Dynamic Model ◽  
Circulatory System ◽  
Operating Conditions ◽  
Time Varying ◽  
Outlet Port ◽  
Mock Circulatory System ◽  
Linear Resistance ◽  
Wide Range ◽  
Artificial Ventricle ◽  
Nonlinear Resistance

Inlet and outlet pressures and flows were obtained over a wide range of operating conditions for a pneumatically driven sac-type artificial ventricle connected to a mechanical mock circulatory system. The load presented to the ventricle by the mock circulatory system was found to be characterized by a linear resistance and capacitance. A dynamic model for the ventricle which accounted for instantaneous pressures and flows was developed. The outlet port is characterized by an inertance and square law resistance; the inlet port is characterized by a nonlinear resistance dependent on the type of valve. The input to the model is the time varying sac pressure. The model predicts the fill-limited and ejection-limited modes of the artificial ventricle.

The instability of the thin vortex ring of constant vorticity

1977 ◽  
Vol 287 (1344) ◽  
pp. 273-305 ◽  
Keyword(s):  
Stability Analysis ◽  
Vortex Ring ◽  
Mean Flow ◽  
Bending Waves ◽  
Constant Vorticity ◽  
Ring Radius ◽  
Amplification Rate ◽  
The Mean ◽  
The Stability ◽  
Good Agreement

A theoretical investigation of the instability of a vortex ring to short azimuthal bending waves is presented. The theory considers only the stability of a thin vortex ring with a core of constant vorticity (constant /r) in an ideal fluid. Both the mean flow and the disturbance flow are found as an asymptotic solution in e = a /R, the ratio of core radius to ring radius. Only terms linear in wave amplitude are retained in the stability analysis. The solution to 0 (e 2 ) is presented, although the details of the stability analysis are carried through completely only for a special class of bending waves that are known to be unstable on a line filament in the presence of strain (Tsai & Widnall 1976) and have been identified in the simple model of Widnall, Bliss & Tsai (1974) as a likely mode of instability for the vortex ring: these occur at certain critical wavenumbers for which waves on a line filament of the same vorticity distribution would not rotate (w 0 = 0). The ring is found to be always unstable for at least the lowest two critical wavenumbers ( ka = 2.5 and 4.35). The amplification rate and wavenumber predicted by the theory are found to be in good agreement with available experimental results.

scholarly journals Numerical and experimental investigation of the mean and turbulent characteristics of a wing-tip vortex in the near field

2014 ◽  
Vol 228 (13) ◽  
pp. 2516-2529 ◽  
Author(s):  
Micheál S O’Regan ◽  
Philip C Griffin ◽  
Trevor M Young
Keyword(s):  
Reynolds Stress ◽  
Turbulence Model ◽  
Near Field ◽  
Tip Vortex ◽  
Mean Flow ◽  
Turbulent Characteristics ◽  
The Mean ◽  
Wing Tip Vortex ◽  
Wing Tip ◽  
Good Agreement

The near-field (up to three chord lengths) development of a wing-tip vortex is investigated both numerically and experimentally. The research was conducted in a medium speed wind tunnel on a NACA 0012 square tip half-wing at a Reynolds number of 3.2 × 105. A full Reynolds stress turbulence model with a hybrid unstructured grid was used to compute the wing-tip vortex in the near field while an x-wire anemometer and five-hole probe recorded the experimental results. The mean flow of the computed vortex was in good agreement with experiment as the circulation parameter was within 6% of the experimental value at x/ c = 0 for α = 10° and the crossflow velocity magnitude was within 1% of the experimental value at x/ c = 1 for α = 5°. The trajectory of the computed vortex was also in good agreement as it had moved inboard by the same amount (10% chord) as the experimental vortex at the last measurement location. The axial velocity excess is under predicted for α = 10°, whereas the velocity deficit is in relatively good agreement for α = 5°. The computed Reynolds shear stress component 〈 u′v′〉 is in good agreement with experiment at x/ c = 0 for α = 5°, but is greatly under predicted further downstream and at all locations for α = 10°. It is thought that a lack of local grid refinement in the vortex core and deficiencies in the Reynolds stress turbulence model may have led to errors in the mean flow and turbulence results respectively.

Vortex Shedding and Lock-On in a Perturbed Flow

1993 ◽  
Vol 115 (2) ◽  
pp. 283-291 ◽  
Author(s):  
Mary S. Hall ◽  
Owen M. Griffin
Keyword(s):  
Vortex Shedding ◽  
Bluff Body ◽  
Reynolds Numbers ◽  
Vortex Street ◽  
Mean Flow ◽  
Strong Resonance ◽  
Resonance Flow ◽  
The Mean ◽  
Rotational Oscillations ◽  
Good Agreement

Vortex shedding resonance or lock-on is observed when a bluff body is placed in an incident mean flow with a superimposed periodic component. Direct numerical simulations of this flow at a Reynolds number of 200 are compared here with experiments that have been conducted by several investigators. The bounds of the lock-on or resonance flow regimes for the computations and experiments are in good agreement. The computed and measured vortex street wavelengths also are in good agreement with experiments at Reynolds numbers from 100 to 2000. Comparison of these computations with experiments shows that both natural, or unforced, and forced vortex street wakes are nondispersive in their wave-like behavior. Recent active control experiments with rotational oscillations of a circular cylinder find this same nondispersive behavior over a three-fold range of frequencies at Reynolds numbers up to 15,000. The vortex shedding and lock-on resulting from the introduction of a periodic inflow component upon the mean flow exhibit a particularly strong resonance between the imposed perturbations and the vortices.

Twin Inclined Circular Jets Evolution Through a Cool Crossflow

2007 ◽  
Author(s):  
Amina Radhouane ◽  
Nejla Mahjoub Sai¨d ◽  
Hatem Mhiri ◽  
George Lepalec ◽  
Philippe Bournot
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Mean Flow ◽  
Navier Stokes Equations ◽  
Vortical Structures ◽  
Circular Jets ◽  
Turbulent Closure ◽  
The Mean ◽  
Good Agreement

The aim of this paper is to examine experimentally as well as numerically the flowfield resulting from the interaction between a twin circular inclined hot jets emerging into a cooling crossflow. The resulting flowfield is quite complex due to the presence of different vortical structures including the kidney vortex, the horse-shoe vortex, etc... The evolution of the twin inclined jets through the crossflow could be depicted by tracking the mean-flow velocity field and its associated turbulence statistics by means of the PIV technique. This evolution can be influenced by many factors. Herein, we will deal with that resulted by the injection nozzles’ inclination and the jets’ spacing. Then, we performed a three dimensional sample of the studied configuration in order to simulate the evolution of the resulting flowfield. For that, the Navier Stokes equations were simulated with an RSM second order turbulent closure model. Then a non uniform meshing was applied. A good agreement was obtained between the experimental data and the numerical modeling. After validation we could represent in addition to the available results, the temperature distribution and the effects the variation of the injection inclination and that of the jets’ spacing bring on it (on its spatial evolution).

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