Closure to “Discussions of ‘A Quasi Method of Characteristics With Application to Fluid Lines With Frequency Dependent Wall Shear and Heat Transfer’” (1969, ASME J. Basic Eng., 91, pp. 226–227)

1969 ◽  
Vol 91 (2) ◽  
pp. 227-227
Author(s):  
F. T. Brown
Keyword(s):  
Heat Transfer ◽  
Method Of Characteristics ◽  
Frequency Dependent ◽  
Wall Shear

A Quasi Method of Characteristics With Application to Fluid Lines With Frequency Dependent Wall Shear and Heat Transfer

1969 ◽  
Vol 91 (2) ◽  
pp. 217-226 ◽  
Author(s):  
F. T. Brown
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Partial Differential Equations ◽  
Differential Equations ◽  
Method Of Characteristics ◽  
Hyperbolic Partial Differential Equations ◽  
Unsteady Fluid Flow ◽  
Wall Shear ◽  
Unsteady Fluid ◽  
Or History

The method of characteristics has been used in a variety of graphical, analytical, and numerical ways as a powerful tool in the solution of hyperbolic partial differential equations. The availability of digital computers permits the basic method to be applied to a greatly extended class of problems represented by semihyperbolic equations. This general extension is illustrated by problems of unsteady fluid flow in rigid tubes with the effects of frequency or history-dependent wall shear and heat transfer.

Flow and Thermal Fields in a Pendant Droplet Moving on Lyophobic Surface

2010 ◽  
Author(s):  
Basant Singh Sikarwar ◽  
K. Muralidhar ◽  
Sameer Khandekar
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Reynolds Number ◽  
Shear Stress ◽  
Heat Transfer Coefficient ◽  
Wall Shear Stress ◽  
Transfer Coefficient ◽  
Maximum Shear Stress ◽  
Computational Domain ◽  
Wall Shear

Clusters of liquid drops growing and moving on physically or chemically textured lyophobic surfaces are encountered in drop-wise mode of vapor condensation. As opposed to film-wise condensation, drops permit a large heat transfer coefficient and are hence attractive. However, the temporal sustainability of drop formation on a surface is a challenging task, primarily because the sliding drops eventually leach away the lyophobicity promoter layer. Assuming that there is no chemical reaction between the promoter and the condensing liquid, the wall shear stress (viscous resistance) is the prime parameter for controlling physical leaching. The dynamic shape of individual droplets, as they form and roll/slide on such surfaces, determines the effective shear interaction at the wall. Given a shear stress distribution of an individual droplet, the net effect of droplet ensemble can be determined using the time averaged population density during condensation. In this paper, we solve the Navier-Stokes and the energy equation in three-dimensions on an unstructured tetrahedral grid representing the computational domain corresponding to an isolated pendant droplet sliding on a lyophobic substrate. We correlate the droplet Reynolds number (Re = 10–500, based on droplet hydraulic diameter), contact angle and shape of droplet with wall shear stress and heat transfer coefficient. The simulations presented here are for Prandtl Number (Pr) = 5.8. We see that, both Poiseuille number (Po) and Nusselt number (Nu), increase with increasing the droplet Reynolds number. The maximum shear stress as well as heat transfer occurs at the droplet corners. For a given droplet volume, increasing contact angle decreases the transport coefficients.

Boundary Layer Closure and Heat Transfer in Constant Base Pressure and Simple Wave Guns

1978 ◽  
Vol 100 (4) ◽  
pp. 690-696 ◽  
Author(s):  
A. D. Anderson ◽  
T. J. Dahm
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Method Of Characteristics ◽  
Simple Wave ◽  
Momentum Equation ◽  
Base Pressure ◽  
Two Dimensional ◽  
The Method Of Characteristics

Solutions of the two-dimensional, unsteady integral momentum equation are obtained via the method of characteristics for two limiting modes of light gas launcher operation, the “constant base pressure gun” and the “simple wave gun”. Example predictions of boundary layer thickness and heat transfer are presented for a particular 1 in. hydrogen gun operated in each of these modes. Results for the constant base pressure gun are also presented in an approximate, more general form.

The Frequency Response of Electrochemical Wall Shear Probes in Pulsatile Flow

1987 ◽  
Vol 109 (1) ◽  
pp. 60-64 ◽  
Author(s):  
L. Talbot ◽  
J. J. Steinert
Keyword(s):  
Mass Transfer ◽  
Frequency Response ◽  
Pulsatile Flow ◽  
Straight Tube ◽  
Asymptotic Results ◽  
Frequency Dependent ◽  
Shear Rates ◽  
Pulsatile Flows ◽  
Wall Shear ◽  
Good Agreement

The frequency response of surface-mounted electrochemical mass transfer probes used to deduce wall shear rates has been investigated experimentally for the case of fully developed laminar pulsatile flow in a straight tube. Generally good agreement is found with the asymptotic results obtained by Lighthill’s methods. The significance of the results with regard to the investigation of models of pulsatile flows of physiological interest is discussed. It is concluded that the frequency-dependent phase and amplitude corrections required to obtain accurate wall shear measurements are of such magnitudes as to render impractical the use of electrochemical probes to determine wall shear rates in these flows.

An Efficient Method for Simulating Frequency-Dependent Friction in Transient Liquid Flow

1975 ◽  
Vol 97 (1) ◽  
pp. 97-105 ◽  
Author(s):  
A. K. Trikha
Keyword(s):  
Liquid Flow ◽  
Method Of Characteristics ◽  
Computation Time ◽  
Approximate Expression ◽  
Test System ◽  
Exact Expression ◽  
Frequency Dependent ◽  
Efficient Procedure ◽  
Liquid Line ◽  
Frequency Domains

An efficient procedure is developed for simulating frequency-dependent friction in transient laminar liquid flow by the method of characteristics. The procedure consists of determining an approximate expression for frequency-dependent friction such that the use of this expression requires much less computer storage or computation time than the use of the exact expression. The derived expression for frequency-dependent friction approximates the exact expression very well in both time and frequency domains. Calculated results for a test system are compared with the experimental results so show that the approximate expression predicts accurately the surge pressures, pressure wave distortion as well as pressure attenuation in a liquid line.

Study on the Characteristics of Flow and Heat Transfer of Polymeric-Fluid-Based Cu Nanofluids

2017 ◽  
Author(s):  
Weihua Cai ◽  
Yongyao Li ◽  
Yue Wang ◽  
Xin Zheng ◽  
Mengsheng Zhu
Keyword(s):  
Heat Transfer ◽  
Aqueous Solution ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Drag Reduction ◽  
Volume Fraction ◽  
Solution Flow ◽  
Flow And Heat Transfer ◽  
Wall Shear ◽  
Polymer Aqueous Solution

In this paper, we propose a new fluid: drag-reducing-fluid-based nanofluids (DRFBN), i.e., nanoparticles are added into polymer aqueous solution. In order to investigate the flow and heat transfer characteristics of this new fluid, the Reynolds stress turbulence model and equivalent viscosity model are used in the simulations. Wall shear stress and Nusselt number (Nu) are chosen to represent the effects of drag reduction and heat enhancement respectively. The numerical studies mainly focus on the effects of different parameters on wall shear stress and Nu. The results show that comparison with water flow, DRFBN flow still has remarkable drag-reducing effect; comparison with polymer aqueous solution flow, DRFBN flow has some improvement on heat transfer. Therefore, DRFBN has duel effects: drag reduction and heat transfer enhancement. Besides, it is found that the parameters of nanoparticle volume fraction, Reynolds number and drag-reducing parameter have remarkable effects on wall shear stress and Nu of DRFBN flow.

Effect of the Broken Rib Locations on the Heat Transfer and Fluid Flow in a Rotating Latticework Duct

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Wei Du ◽  
Lei Luo ◽  
Songtao Wang ◽  
Jian Liu ◽  
Bengt Sunden
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Nusselt Number ◽  
Wall Shear Stress ◽  
Flow Structure ◽  
Suction Side ◽  
Spiral Flow ◽  
Numerical Studies ◽  
Rotational Number ◽  
Wall Shear

AbstractA numerical method was used to study the effect of the broken rib locations on the heat transfer and flow structure in the latticework duct with various rotational numbers. The latticework duct had eleven subchannels on both the pressure side and the suction side. The crossing angle for each subchannel was 45 deg. The numerical studies were conducted with five different broken rib locations and six rotational numbers (0–0.5). The Reynolds number was fixed as 44,000. The flow structure, wall shear stress, and Nusselt number distributions were analyzed. It was found that the upward spiral flow and helical flow dominated the flow structure in the latticework duct. In addition, the impingement region (at the beginning of the subchannel) induced by the upward spiral flow was responsible for the high Nusselt number and wall shear stress. After adoption of the broken rib in the latticework duct, the Nusselt number was increased by 6.12% on the pressure endwall surface and increased by 6.02% on the rib surface compared to the traditional latticework duct. As the rotational number was increased, the Nusselt number on the pressure endwall surface was decreased by up to 5.4%. However, the high rotational number enhanced the heat transfer on the suction side. The high rotational number also decreased the friction factor in the latticework duct. Furthermore, the overall thermal performance was increased by 12.12% after adoption of the broken ribs on both the turn region and the impingement region.

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