Laminar Combined Convection From a Rotating Cone

1963 ◽  
Vol 85 (1) ◽  
pp. 29-34 ◽  
Author(s):  
R. G. Hering ◽  
R. J. Grosh
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Convection ◽  
Numerical Solutions ◽  
Temperature Fields ◽  
Boundary Layer Equations ◽  
Experimental Heat ◽  
Experimental Heat Transfer ◽  
Cone Apex ◽  
Rotating Cone

The effect of free convection on heat transfer and on the flow field about a rotating cone is studied. A similar solution for the laminar boundary-layer equations is found to exist when the cone surface temperature varies linearly with distance from the cone apex. The transformed boundary-layer equations contain the important parameter Gr/Re2. This parameter determines the relative importance of the free convection motions on forced convection. Numerical solutions of the transformed equations for aiding flows have been carried out for Prandtl number 0.7 and different values of Gr/Re2. Results are reported for the heat transfer, shear stress, shaft moment, and velocity and temperature fields. Criteria are given for subdividing the regimes of flow as purely free, purely forced, and combined flow. Preliminary experimental heat-transfer results are reported which indicate the trends predicted by theory.

Keller-Box Scheme to Mixed Convection Flow Over a Solid Sphere with the Effect of MHD

2021 ◽  
Vol 6 (1) ◽  
pp. 97
Author(s):  
Mohammad Ghani ◽  
Wayan Rumite
Keyword(s):  
Boundary Layer ◽  
Free Convection ◽  
Mixed Convection ◽  
Numerical Solutions ◽  
Solid Sphere ◽  
Convection Flow ◽  
Boundary Layer Equations ◽  
Buoyancy Forces ◽  
Dimensional Boundary ◽  
External Forces

Mixed convection is the combination of a free convection caused by the buoyancy forces due to the different density and a forced convection due to external forces that increase the heat exchange rate. This means that, in free convection, the effect of external forces is significant besides buoyancy forces. In this study the fluid type with viscoelastic effect is non-Newtonian. The viscoelastic fluids that pass over a surface of a sphere form a thin layer, which due to their dominant viscosity is called by the border layer. The obtained limiting layer is analyzed with the thickness of the boundary layer-  near the lower stagnating point, then obtained dimensional boundary layer equations, continuity, momentum, and energy equations. These dimensional boundary layer equations are then transformed into non-dimensional boundary layer equations by using non-dimensional variables. Further, the non-dimensional boundary layer equations are transformed into ordinary differential equations by using stream function, so that obtained the non-similar boundary layer equations. These non-similar boundary layer equations are solved numerically by using finite difference method of Keller-Box. The discretization results are non-linear and it should be linearized using newton linearization technique. The numerical solutions are analyzed the effect of Prandtl number, viscoelastic, mixed convection, and MHD parameters towards velocity profile, temperature profile, and wall temperature.

On free convection experiments in inclined air layers heated from below

1980 ◽  
Vol 96 (3) ◽  
pp. 461-479 ◽  
Author(s):  
Douglas W. Ruth ◽  
K. G. T. Hollands ◽  
G. D. Raithby
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Convective Motion ◽  
Secondary Transition ◽  
Transfer Data ◽  
Experimental Heat ◽  
Experimental Heat Transfer ◽  
Air Layers ◽  
Rayleigh Numbers ◽  
Theory And Experiment

The heat transfer and free convective motion, in inclined air layers heated from below, for angles of incidence 0 [les ] ϕ [les ] 30°, and Rayleigh numbers 100 < Ra cos ϕ < 10000, are studied experimentally. Results of both heat-transfer measurements and flow-visualization studies are reported. The purpose of the study was to investigate the fact, first noted by Hollands et al. (1976), that the experimental heat-transfer data, for ϕ > 20°, is not a function of the product Ra cos ϕ only, as expected from theoretical consideration. This discrepancy between theory and experiment is here attributed to a hypothesized secondary transition in the convective motion, due primarily to perturbation velocities in the upslope direction. This secondary transition appears to be the same as that predicted theoretically by Clever & Busse (1977); qualitative agreement with their theory is observed.

The effect of convective heat transfer on unsteady boundary-layer separation

2001 ◽  
Vol 428 ◽  
pp. 107-131 ◽  
Author(s):  
K. W. CASSEL
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Inclination Angle ◽  
Numerical Solutions ◽  
Heated Surface ◽  
Boundary Layer Separation ◽  
Convection Boundary Layer ◽  
Grashof Number ◽  
Boundary Layer Equations ◽  
Unsteady Mixed Convection

The unsteady evolution of a boundary layer induced by a rectilinear vortex convecting above a heated surface is considered numerically. This model problem is representative of the types of interactions that can occur when vortices encounter solid surfaces in a wide variety of diverse applications involving high-Reynolds-number and high-Grashof-number flows. It is known that in the case without heat transfer, the vortex-induced boundary layer evolves toward a singularity as it forms a sharp spike that erupts away from the surface. Numerical solutions of the unsteady mixed-convection boundary-layer equations in the Boussinesq limit are obtained in Lagrangian coordinates. Solutions for various values of the inclination angle of the surface and Grashof number show that the coupling between the fluid flow and heat transfer can have a dramatic effect upon the transport of momentum and energy within the boundary layer induced by the vortex. The unsteady eruption convects high-temperature, near-wall fluid away from the surface and causes large gradients in the thermal boundary layer. The buoyancy force acting on the heated boundary-layer fluid can also have a significant impact on the unsteady separation process, either accelerating or delaying it, depending upon the inclination angle of the surface.

scholarly journals The Effect of Plate Oscillations on Horizontal Free Convection Flow

1977 ◽  
Vol 30 (3) ◽  
pp. 335 ◽  
Author(s):  
RL Verma ◽  
Punyatma Singh
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Convection ◽  
Skin Friction ◽  
Low Frequency ◽  
Convection Flow ◽  
Phase Lag ◽  
Mean Flow ◽  
Free Convection Flow ◽  
Boundary Layer Equations

The free convection flow along a semi-infinite horizontal plate oscillating in its own plane is analysed The basic flow is purely buoyancy induced, while the oscillations in the plate cause a time-dependent boundary layer flow and heat transfer. The boundary layer equations are linearized and the first two approximations are considered. Two separate solutions valid for high and low frequency ranges are obtained by a series expansion in terms of frequency parameters. The skin friction and the rate of heat transfer are studied for both frequency ranges. For very high frequencies, the oscillatory flow pattern is of a 'shear-wave' type, unaffected by the mean flow. It is found that the phase of the skin friction at the plate lags that of the plate oscillations by in and the rate of heat transfer has a phase lag of 1/2n.

Experimental Heat Transfer Investigation in a Multisplitter LP Vane Architecture

2010 ◽  
Author(s):  
V. Pinilla ◽  
J. P. Solano ◽  
G. Paniagua ◽  
S. Lavagnoli ◽  
T. Yasa
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Pressure Ratio ◽  
Transition To Turbulence ◽  
Time Resolved ◽  
Experimental Heat ◽  
Experimental Heat Transfer ◽  
Flow Features ◽  
Aero Engines ◽  
Layered Thin Film

This paper reports the external convective heat transfer in an innovative low pressure vane with multisplitter configuration. Three small aerodynamic blades are positioned between each structural vane, providing a novel architecture for ultra-high by-pass ratio aero-engines, with increased LP vane radius and swan-neck diffuser to link the HP turbine. The measurements have been performed in the compression tube test rig of the von Karman Institute, using single layered thin film gauges. Time-averaged and time-resolved heat transfer distributions are presented for the three aerovanes and for the structural blade, at three pressure ratios tested at representative conditions of modern aeroengines, with M2,is ranging from 0.87 to 1.07 and a Reynolds number of about 106. This facility is specially suited to control the gas-to-wall temperature ratio. Accurate time-averaged heat transfer distributions around the aerovanes are assessed, that allow characterizing the boundary layer status for each position and pressure ratio. The heat transfer distribution around the structural blade is also obtained, depicting clear transition to turbulence, as well as particular flow features on the pressure side, like separation bubbles. Unsteady data analysis reveals the destabilizing effect of the rotor left-running shock on the aerovanes boundary layer, as well as the shift of transition onset for different blade passing events.

Laminar Boundary∼Layer Free Convection along an Inclined, Isothermal Surface

1972 ◽  
Vol 1 (4) ◽  
pp. 189-196 ◽  
Author(s):  
J.B. Lee ◽  
G.S.H. Lock
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Convection ◽  
Laminar Boundary Layer ◽  
Theoretical Consideration ◽  
Plane Surface ◽  
Convection Flow ◽  
Inclined Plane ◽  
Free Convection Flow ◽  
Boundary Layer Equations

This paper gives theoretical consideration to the problem of laminar, boundary-layer, free convection flow along a long, inclined, plane surface heated isothermally. Development of the appropriate boundary-layer equations is followed by their numerical solution for air. The effects of inclination and position on heat transfer and the temperature, pressure and velocity profiles are presented graphically for RaL ≤ 106.

A singularity in thermal boundary-layer flow on a horizontal surface

1992 ◽  
Vol 242 ◽  
pp. 419-440 ◽  
Author(s):  
P. G. Daniels
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Thermal Boundary Layer ◽  
Numerical Solutions ◽  
Rational Numbers ◽  
Velocity Fields ◽  
Boundary Layer Equations ◽  
Layer Flow ◽  
Buoyancy Flows ◽  
Temperature And Velocity Fields

A thermal boundary layer, in which the temperature and velocity fields are coupled by buoyancy, flows along a horizontal, insulated wall. For sufficiently low local Froude number the solution terminates in a singularity with rising skin friction and falling pressure. The structure of the singularity is obtained and the results are compared with numerical solutions of the horizontal boundary-layer equations. A novel feature of the analysis is that the powers of the streamwise coordinate involved in the structure of the singularity do not appear to be simple rational numbers and are determined from the solution of a pair of ordinary differential equations which govern the flow in an inner viscous region close to the wall. Modifications of the theory are noted for cases where either the temperature or a non-zero heat transfer are specified at the wall.

scholarly journals Pressure Work Effect on Natural Convection Flow from a Vertical Circular Cone with Suction and Non-Uniform Surface Temperature

1970 ◽  
Vol 36 ◽  
pp. 6-11 ◽  
Author(s):  
MA Alim ◽  
Md M Alam ◽  
Md MK Chowdhury
Keyword(s):  
Boundary Layer ◽  
Temperature Gradient ◽  
Free Convection ◽  
Surface Temperature ◽  
Numerical Solutions ◽  
Circular Cone ◽  
Convection Flow ◽  
Transfer Velocity ◽  
Pressure Work ◽  
Boundary Layer Equations

Laminar free convection from a vertical circular cone maintained at non-uniform surface temperature with effects of suction and pressure work are considered. Non-similarity solutions for boundary layer equations are found to exist when the surface temperature follows the power law variations with the distance measured from the leading edge. The numerical solutions of the transformed non-similar boundary layer equations are obtained by using a finite difference method with Keller Box scheme. Solutions obtained in terms of skin-friction, local rate of heat transfer, velocity and temperature profiles for the values of Prandtl number, pressure work parameter and temperature gradient are displayed in both graphical and tabular forms.Keywords: Free convection, Viscous dissipation, Boussinesq approximation, Temperature gradient, Pressure work.Journal of Mechanical Engineering Vol.36 Dec. 2006 pp.6-11DOI = 10.3329/jme.v36i0.805

Sign in / Sign up

Export Citation Format

Share Document