scholarly journals Experimental Verification of Modeled Thermal Distribution Produced by a Piston Source in Physiotherapy Ultrasound

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
M. I. Gutierrez ◽  
S. A. Lopez-Haro ◽  
A. Vera ◽  
L. Leija
Keyword(s):  
Acoustic Field ◽  
Temperature Profiles ◽  
Acoustic Intensity ◽  
Fe Method ◽  
Thermal Distribution ◽  
Temperature Modeling ◽  
Temperature Distributions ◽  
Acoustic Profile ◽  
Thermal Patterns ◽  
The Ideal

Objectives. To present a quantitative comparison of thermal patterns produced by the piston-in-a-baffle approach with those generated by a physiotherapy ultrasonic device and to show the dependency among thermal patterns and acoustic intensity distributions.Methods. The finite element (FE) method was used to model an ideal acoustic field and the produced thermal pattern to be compared with the experimental acoustic and temperature distributions produced by a real ultrasonic applicator. A thermal model using the measured acoustic profile as input is also presented for comparison. Temperature measurements were carried out with thermocouples inserted in muscle phantom. The insertion place of thermocouples was monitored with ultrasound imaging.Results. Modeled and measured thermal profiles were compared within the first 10 cm of depth. The ideal acoustic field did not adequately represent the measured field having different temperature profiles (errors 10% to 20%). Experimental field was concentrated near the transducer producing a region with higher temperatures, while the modeled ideal temperature was linearly distributed along the depth. The error was reduced to 7% when introducing the measured acoustic field as the input variable in the FE temperature modeling.Conclusions. Temperature distributions are strongly related to the acoustic field distributions.

An Energy Boundary Element Formulation for Predicting the Acoustic Field Around a Vehicle at High Frequencies Due to Airborne Noise Sources

2003 ◽  
Author(s):  
Aimin Wang ◽  
Nickolas Vlahopoulos ◽  
Jason Zhu ◽  
Mike Qian
Keyword(s):  
Energy Density ◽  
Boundary Element ◽  
Acoustic Field ◽  
Test Data ◽  
Acoustic Energy ◽  
Element Formulation ◽  
Acoustic Intensity ◽  
Numerical Predictions ◽  
Airborne Noise ◽  
Acoustic Energy Density

An Energy Boundary Element Analysis (EBEA) formulation is presented for calculating sound radiation from a source with arbitrary shape at high frequency. The basic integral equation for the EBEA is derived including a half-space boundary condition. The time and frequency averaged acoustic energy density and acoustic intensity constitutes the primary variables of the new formulation, and the corresponding Green’s functions are derived. The governing equations for the EBEA are established and the numerical formulae for the coefficients of the system matrix, the acoustic energy density, and the acoustic intensity are derived using a Gaussian quadrature. The EBEA formulation and the corresponding numerical implementation are validated by comparing EBEA results to test data for the acoustic field around a vehicle that originates from an airborne noise source. Good correlation is demonstrated between numerical predictions and test data.

scholarly journals On the Thermal Regime of an Arctic Valley Glacier: A Study of White Glacier, Axel Heiberg Island, N.W.T., Canada

1987 ◽  
Vol 33 (114) ◽  
pp. 200-211 ◽  
Author(s):  
Heinz Blatter
Keyword(s):  
Climatic Conditions ◽  
Temperature Profiles ◽  
Two Dimensional ◽  
Temperature Minimum ◽  
Climatic Warming ◽  
Simple Scheme ◽  
Glacier Surface ◽  
Temperature Distributions ◽  
Valley Glacier ◽  
Simple Numerical Model

AbstractFrom 1974 to 1981, a total of 32 bore holes was drilled on White Glacier and vertical ice-temperature profiles measured. The data obtained allowed the construction of three longitudinal and four transverse profiles of the two-dimensional temperature distributions. Thus, an extensive layer of temperate or near-temperate ice was discovered close to the bedrock in the lowest part of the glacier tongue. It was also found that the temperature distribution cannot be in a steady state, since there is a temperature minimum 100–150 m below the glacier surface in the accumulation area. A simple numerical model calculation shows that this minimum can be mostly explained by the general climatic warming since 1880. The 10 m temperatures show diffuse relations to climatic conditions and balance zones. A simple scheme for extrapolating “surface temperatures” is discussed.

scholarly journals On the Thermal Regime of an Arctic Valley Glacier: A Study of White Glacier, Axel Heiberg Island, N.W.T., Canada

1987 ◽  
Vol 33 (114) ◽  
pp. 200-211 ◽  
Author(s):  
Heinz Blatter
Keyword(s):  
Climatic Conditions ◽  
Temperature Profiles ◽  
Two Dimensional ◽  
Temperature Minimum ◽  
Climatic Warming ◽  
Simple Scheme ◽  
Glacier Surface ◽  
Temperature Distributions ◽  
Valley Glacier ◽  
Simple Numerical Model

AbstractFrom 1974 to 1981, a total of 32 bore holes was drilled on White Glacier and vertical ice-temperature profiles measured. The data obtained allowed the construction of three longitudinal and four transverse profiles of the two-dimensional temperature distributions. Thus, an extensive layer of temperate or near-temperate ice was discovered close to the bedrock in the lowest part of the glacier tongue. It was also found that the temperature distribution cannot be in a steady state, since there is a temperature minimum 100–150 m below the glacier surface in the accumulation area. A simple numerical model calculation shows that this minimum can be mostly explained by the general climatic warming since 1880. The 10 m temperatures show diffuse relations to climatic conditions and balance zones. A simple scheme for extrapolating “surface temperatures” is discussed.

Benchmark Solution for the Prediction of Temperature Distributions During Radiofrequency Ablation of Cardiac Tissue

2004 ◽  
Vol 126 (4) ◽  
pp. 519-522 ◽  
Author(s):  
Ryan T. Roper and ◽  
Matthew R. Jones
Keyword(s):  
Cardiac Tissue ◽  
Numerical Solutions ◽  
Integral Transforms ◽  
Tissue Temperature ◽  
Temperature Profiles ◽  
Bioheat Equation ◽  
Temperature Distributions ◽  
Axial Temperature ◽  
Program Temperature ◽  
Benchmark Solution

Several studies on radiofrequency (RF) ablation are aimed at accurately predicting tissue temperature distributions by numerical solution of the bioheat equation. This paper describes the development of a solution that can serve as a benchmark for subsequent numerical solutions. The solution was obtained using integral transforms and evaluated using a C program. Temperature profiles were generated at various times and for different convection coefficients. In addition, a numerical model was developed using the same assumptions made in obtaining the benchmark solution. Comparison of surface and axial temperature profiles shows that the two solutions match very closely, cross validating the numerical methods used in evaluating both solutions.

Manipulation of Microfluidic Flows Using Time Dependent Wall Temperatures

2004 ◽  
Author(s):  
Tom Mautner
Keyword(s):  
Thermal Diffusion ◽  
Wall Temperature ◽  
Lattice Boltzmann ◽  
Channel Wall ◽  
Three Dimensional ◽  
Temperature Profiles ◽  
Thermal Coupling ◽  
Uniform Temperature ◽  
Temperature Distributions ◽  
Flow Through

One module in a bioagent detector currently under development involves a flow-through PCR module [1] [3] [4]. Conventional, flow-through PCR devices utilize three heaters to obtain the required temperatures in each zone, the length of which is specified by the required sample residence times. An alternate design uses two wall heaters with substrate conduction supplying the center zone temperature. The concept of using a conduction based PCR device led to an extensive computational study of various channel wall temperature profiles that would produce enhanced mixing in a variety of microfluidic devices. The results are applicable to micro channel designs in general even tough motivated by the conduction based PCR configuration. The lattice Boltzmann (LB) method was used to perform low Reynolds number (typically Re=0.10) simulations for two and three dimensional channel geometries having various wall temperature distributions. The momentum and thermal lattice Boltzmann equations were coupled via a body force term in the momentum equation. Initial computations using two- and three-heater configurations in two dimensions demonstrated excellent comparisons with published data provided that both the top and bottom walls were heated. If only one wall was heated, large vertical thermal gradients occurred resulting in non-uniform temperature fields. However, when the same conditions were applied to three dimensional channels, lower temperatures were observed in the center of the channel regardless of the wall temperatures or channel aspect ratio. Parametric studies were performed to evaluate the effects of thermal coupling, thermal diffusion coefficients, entrance temperatures, wall temperature configurations and channel geometry. If was found that moderate variation of the thermal diffusion coefficient produced only minor differences in the temperature field, and large changes in the thermal coupling magnitude demonstrated transition from natural to forced convection flows. The simulations also indicate that the largest effect on flow and temperature uniformity arises from the applied wall temperature distribution (various thickness channel walls). It was found, in 2D, that if the channel wall starts from ambient temperature, the applied heating, on the outer surfaces only, may not result in the desired wall or fluid temperatures. However, once the channel walls are heated to a uniform temperature, excellent temperature distributions are obtained for both thick and thin channel walls. Additionally, a checkerboard pattern of wall heaters was used to test its application to promoting mixing. Results were favorable in creating enhanced mixing; however, the temperature pattern did not produce uniform temperature profiles in the channel.

Thermal Modeling of a Small-Particle Solar Central Receiver

2000 ◽  
Vol 122 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Fletcher J. Miller ◽  
Roland W. Koenigsdorff
Keyword(s):  
Thermal Model ◽  
Energy Equation ◽  
Three Dimensional ◽  
Temperature Profiles ◽  
Radiation Model ◽  
Carbon Particles ◽  
Temperature Distributions ◽  
Central Receiver ◽  
Type Particle ◽  
Very High

This paper presents a thermal model of a solar central receiver that volumetrically absorbs concentrated sunlight directly in a flowing gas stream seeded with submicron carbon particles. A modified six-flux radiation model is developed and used with the energy equation to calculate the three-dimensional radiant flux and temperature distributions in a cavity-type particle receiver. Results indicate that the receiver is capable of withstanding very high incident fluxes and delivering high temperatures. The receiver efficiency as a function of mass flow rate as well as the effect of particle oxidation on the temperature profiles are presented. [S0199-6231(00)00201-X]

Application of Brillouin Fiber Optic Sensors to Monitor Pipeline Integrity

2004 ◽  
Author(s):  
R. C. Tennyson ◽  
W. D. Morison ◽  
B. Colpitts ◽  
A. Brown
Keyword(s):  
Optical Fibers ◽  
Continuous Monitoring ◽  
Fiber Optic ◽  
Fiber Optic Sensors ◽  
Third Party ◽  
Ground Movement ◽  
Temperature Profiles ◽  
Thermal Anomalies ◽  
Temperature Distributions ◽  
Close Proximity

This paper describes the application of Brillouin fiber optic sensors to monitor pipeline integrity in terms of third party intrusion, leak detection, and ground movement. Brillouin sensors provide a means for continuous monitoring of strain and temperature distributions over distances of about 25km. The optical fibers can be bonded to the pipeline or buried in close proximity to the pipe. Third party intrusion is detected by strain anomalies caused by vehicles or persons in close proximity to the sensor located at some depth below the surface. Leaks from oil or gas pipelines are detected by thermal anomalies in the temperature profiles. Pipeline movement can also be detected using this system for existing and new pipeline installations. Applications include northern pipelines, high consequence areas, river crossings and fault lines.

scholarly journals Studying the effects of strain heating on glacial flow within outlet glaciers from the Heimefrontfjella Range, Dronning Maud Land, Antarctica

2003 ◽  
Vol 37 ◽  
pp. 134-142 ◽  
Author(s):  
Veijo A. Pohjola ◽  
Jim Hedfors
Keyword(s):  
Heat Equation ◽  
Feedback Loop ◽  
Temperature Profiles ◽  
Ice Flow ◽  
One Dimensional ◽  
Ice Surface ◽  
Temperature Distributions ◽  
Dronning Maud Land ◽  
Temporal And Spatial ◽  
Strain Heating

AbstractA one-dimensional numerical thermodynamic model is used to study the effects of strain heating on temperature profiles along the flowline of two outlet glaciers in Dronning Maud Land, Antarctica, flowing down a steep escarpment. Measurements of ice surface velocities on the glaciers show higher speeds than surface speeds calculated using Glen’s flow law. These calculations are based on ice-temperature distributions excluding strain heating in the general heat equation. The incorporation of strain heating in the general heat equation produces higher ice temperatures, and calculated ice surface speeds that are close to the measured values. It is found that relatively short-scale temporal and spatial steps in basal topography are enough to drive the ice flow into a positive feedback loop as long as the bedrock step produces a stress that overcomes the advection of cool ice from the surface. In this case, where surface temperatures are –25°C, stresses of 0.4 MPa are enough to drive the base of the ice to the melting point within 102 years.

Linear and Nonlinear Approach of Hydropneumatic Tensioner Modeling for Spar Global Performance

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Chan K. Yang ◽  
M. H. Kim
Keyword(s):  
Coupling Effect ◽  
Ideal Gas ◽  
Fe Model ◽  
Floating Bodies ◽  
Fe Method ◽  
Stick Slip ◽  
Nonlinear Approach ◽  
The Relationship ◽  
Fully Coupled ◽  
The Ideal

This paper deals with a numerical model of top tension risers with hydropneumatic tensioner for Spar application in the Gulf of Mexico environment. The nonlinearity of the stiffness and the friction characteristics of the tensioner combined with stick-slip behavior of the riser keel joint are investigated. The relationship between tensions and strokes for the hydropneumatic tensioner is based on the ideal gas equation where the isotropic gas constant can be varied to achieve an optimum stroke design based on the tensioner stiffness. Challenges of modeling the coupling effects in the finite element (FE) method between the tensioner and hull motion are also presented. This new FE model is implemented into a fully-coupled time-domain coupled-dynamics-analysis program for floating bodies. The effect of nonlinearity of tensioner curve, tensioner friction, and riser keel friction is intensively investigated. The resultant global motion, TTR stroke, and tensions are systematically compared with those of a simple engineering approach, in which the nonlinear coupling effect is captured by linearization.

Temperature Profiles and Aquifer Mass Transfer in a Circulating Well

1982 ◽  
Vol 104 (1) ◽  
pp. 173-179
Author(s):  
C. A. Oster ◽  
W. A. Scheffler
Keyword(s):  
Mass Transfer ◽  
Temperature Distribution ◽  
Drilling Fluid ◽  
Temperature Profiles ◽  
Formation Water ◽  
Temperature Distributions ◽  
Well Depth

A method is described for determining the temperature distribution in a circulating drilling fluid when aquifers are present in the formation. The depth of an aquifer relative to the well depth is shown to be an important parameter. An aquifer near the surface has much less influence on the temperature distributions than one located near the bottom of the well. If the drilling fluid has much greater density than the entering formation water, then the temperature distributions are altered significantly.

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