scholarly journals A Computational Study on Magnetic Nanoparticles Hyperthermia of Ellipsoidal Tumors

2021 ◽  
Vol 11 (20) ◽  
pp. 9526
Author(s):  
Nickolas D. Polychronopoulos ◽  
Apostolos A. Gkountas ◽  
Ioannis E. Sarris ◽  
Leonidas A. Spyrou
Keyword(s):  
Aspect Ratio ◽  
Computational Model ◽  
Thermal Damage ◽  
Computational Study ◽  
Closed Form Solution ◽  
Magnetic Hyperthermia ◽  
Form Solution ◽  
Aspect Ratios ◽  
Tissue Region ◽  
Spherical Tumor

The modelling of magnetic hyperthermia using nanoparticles of ellipsoid tumor shapes has not been studied adequately. To fill this gap, a computational study has been carried out to determine two key treatment parameters: the therapeutic temperature distribution and the extent of thermal damage. Prolate and oblate spheroidal tumors, of various aspect ratios, surrounded by a large healthy tissue region are assumed. Tissue temperatures are determined from the solution of Pennes’ bio-heat transfer equation. The mortality of the tissues is determined by the Arrhenius kinetic model. The computational model is successfully verified against a closed-form solution for a perfectly spherical tumor. The therapeutic temperature and the thermal damage in the tumor center decrease as the aspect ratio increases and it is insensitive to whether tumors of the same aspect ratio are oblate or prolate spheroids. The necrotic tumor area is affected by the tumor prolateness and oblateness. Good comparison is obtained of the present model with three sets of experimental measurements taken from the literature, for animal tumors exhibiting ellipsoid-like geometry. The computational model enables the determination of the therapeutic temperature and tissue thermal damage for magnetic hyperthermia of ellipsoidal tumors. It can be easily reproduced for various treatment scenarios and may be useful for an effective treatment planning of ellipsoidal tumor geometries.

Study on Contact Melting Inside an Elliptical Tube With Nonisothermal Wall

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Yuansong Zhao ◽  
Wenzhen Chen ◽  
Fengrui Sun
Keyword(s):  
Temperature Distribution ◽  
Aspect Ratio ◽  
Wall Temperature ◽  
Film Theory ◽  
Closed Form Solution ◽  
Cylindrical Tube ◽  
Melting Process ◽  
Contact Melting ◽  
Form Solution ◽  
Basic Equations

The problem of contact melting inside an elliptical tube with nonisothermal wall is investigated. A theoretical model, which the inner wall temperature of source varied with angle ϕ, is established by applying film theory. The basic equations of the melting process are solved theoretically, and a closed-form solution is obtained. Under certain cases, comparisons of results for the melting velocity with those of contact melting inside a horizontal cylindrical tube with nonisothermal wall and an elliptical tube with constant temperature are reported for the validity of the solution in this paper. Effects of aspect ratio J and inner wall temperature distribution are critically assessed. It is found that the smaller the elliptical aspect ratio J is, the greater the effect of wall temperature distribution on melting velocity, and the time to complete melting increases with the augment of coefficient c in temperature distribution.

Natural Convection in a Vertical Annulus Containing Water Near the Density Maximum

1987 ◽  
Vol 109 (4) ◽  
pp. 899-905 ◽  
Author(s):  
D. S. Lin ◽  
M. W. Nansteel
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Density Distribution ◽  
Closed Form ◽  
Closed Form Solution ◽  
Form Solution ◽  
Vertical Flow ◽  
Density Maximum ◽  
Vertical Annulus

Steady natural convection of water near the density extremum in a vertical annulus is studied numerically. Results for flow in annuli with aspect ratio 1≤A≤8 and varying degrees of curvature are given for 103≤Ra≤105. It is shown that both the density distribution parameter R and the annulus curvature K have a strong effect on the steady flow structure and heat transfer in the annulus. A closed-form solution for the vertical flow in a very tall annulus is compared with numerical results for finite-aspect-ratio annuli.

Computational Study of Disk Driven Rotating Flow in a Cylindrical Enclosure

1994 ◽  
Vol 116 (4) ◽  
pp. 815-820 ◽  
Author(s):  
E. Lang ◽  
K. Sridhar ◽  
N. W. Wilson
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Computational Study ◽  
Rotating Disk ◽  
Governing Equations ◽  
Flow Rates ◽  
First Order ◽  
Aspect Ratios ◽  
Torque Coefficient ◽  
Steady Laminar

The problem of steady laminar flow in a stationary cylinder driven by a rotating disk at the top was studied numerically. Three governing equations in cylindrical coordinates were solved by the spatially second-order and temporally first-order accurate ADI method. The flow was characterized by three bulk quantities, namely the torque coefficient and the primary and secondary volumetric flow rates. Calculation of the torque coefficient presented a difficulty because the velocity gradient is singular where the rotating disk and the stationary cylinder meet. This problem was overcome by specifying a gap between the disk and cylinder in the boundary conditions. The results obtained compared favourably with previous experimental results. The relevant parameters for the problem were the rotational Reynolds number, the aspect ratio and the gap. The ranges investigated were as follows: Reynolds number from 1 to 105; aspect ratio from 0.02 to 3; and gap size from 0.1 to 10 percent of the cylinder radius. The results showed that the bulk quantities were dependent on the Reynolds number and the aspect ratio. The torque coefficient was also dependent on the gap, while the volumetric flow rates were only weakly dependent on the gap. For high aspect ratios, the bulk quantities approached constant values.

Flow and Heat Transfer in the Tip-Turn Region of a U-Duct Under Rotating and Non-Rotating Conditions

2011 ◽  
Author(s):  
S.-Y. Hu ◽  
X. Chi ◽  
T. I.-P. Shih ◽  
K. M. Bryden ◽  
M. K. Chyu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Computational Study ◽  
Reynolds Numbers ◽  
Coolant Temperature ◽  
Internal Cooling ◽  
Wall Functions ◽  
Flow And Heat Transfer ◽  
Aspect Ratios ◽  
Turn Region

CFD simulations were performed to study the flow and heat transfer in a U-duct, relevant to internal cooling of the first-stage turbine component in electric-power-generation, gas-turbine engines. Parameters studied include (1) two aspect ratios of the duct cross section, i.e. H/W = 1 and H/W = 0.25; (2) smooth duct and duct lined with pin fins of height H arranged in a staggered fashion; and (3) two rotational speeds: 0 rpm and 3,600 rpm. In all cases, the wall temperature is 1173 K; the coolant temperature at the U-duct inlet is 623 K; and the back pressure at the exit of the U-duct is 25.17 atm. The Reynolds numbers studied are 150,000 for the duct with the 4-to-1 aspect ratio, and 150,000 and 375,000 for the duct with the 1-to-1 aspect ratio. When there is rotation at 3,600 rpm, the rotational numbers corresponding to these Reynolds numbers and duct aspect ratios are 0.592, 1.64, and 4.11, respectively. Result is presented to show the nature of the flow, the temperature distribution, and the surface heat transfer with focus on the flow and heat transfer in the tip-turn region as a function of the parameters investigated. This computational study is based on 3-D steady RANS. The ensemble-averaged continuity, compressible Navier-Stokes, and energy equations were closed by the thermally perfect equation of state with temperature-dependent gas properties and the two-equation realizeable k-ε turbulence model with and without wall functions.

On a Closed-Form Solution of Prandtl's System of Equations

2013 ◽  
Vol 40 (2) ◽  
pp. 106-114
Author(s):  
J. Venetis ◽  
Aimilios (Preferred name Emilios) Sideridis
Keyword(s):  
Closed Form ◽  
Closed Form Solution ◽  
Form Solution ◽  
System Of Equations

Plane Wave Resonance in the Tire Air Cavity as a Vehicle Interior Noise Source

1995 ◽  
Vol 23 (1) ◽  
pp. 2-10 ◽  
Author(s):  
J. K. Thompson
Keyword(s):  
Closed Form Solution ◽  
Form Solution ◽  
Interior Noise ◽  
Cavity Resonance ◽  
Test Results ◽  
Vehicle Interior ◽  
Air Cavity ◽  
Vehicle Interior Noise ◽  
Wave Resonance ◽  
Resonance Frequencies

Abstract Vehicle interior noise is the result of numerous sources of excitation. One source involving tire pavement interaction is the tire air cavity resonance and the forcing it provides to the vehicle spindle: This paper applies fundamental principles combined with experimental verification to describe the tire cavity resonance. A closed form solution is developed to predict the resonance frequencies from geometric data. Tire test results are used to examine the accuracy of predictions of undeflected and deflected tire resonances. Errors in predicted and actual frequencies are shown to be less than 2%. The nature of the forcing this resonance as it applies to the vehicle spindle is also examined.

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