Effect of Linearly Varying Heating Inside a Square Cavity under Natural Convection

Telecommunication devices such as ADSL Modems or Wi-Fi routers are being widely used around the globe. Thermal management of such equipments are of critical importance as the increased power consumptions caused by technological upgrades results in increased heat generation within these systems. The heat transfer process inside such sealed and passively cooled equipments can be simplified as natural convection inside enclosures. Studying actual conditions inside electronic enclosure are necessary for their effective thermal management. This study aims at investigating the effect of non-isothermal heating inside such enclosures with linearly varying temperature distribution on free convection inside square enclosure. The issue of free convection of air interior of a square chamber with linearly varying temperature distributions on the left partition is studied numerically. The effect of change of Rayleigh number, temperature distributions, on flow and temperature field and rate of transfer of heat are analysed. Rayleigh number is chosen to vary in between 103 and 106. Four different cases of linearly varying temperature distributions are considered. The outcomes are presented as stream line plot, isotherm contour and average Nusselt number. The outcomes depicted that case of linearly increasing temperature along the height gives higher Nusselt number than other cases.

Group Analysis of the Plane Steady Vortex Submodel of Ideal Gas with Varying Entropy

The submodel of ideal gas motion being invariant with respect to the time translation and the space translation by one direct has 4 integrals in the case of vortex flows with the varying entropy. The system of nonlinear differential equations of the third order with one arbitrary element was obtained for a stream function and a specific volume. This element contains from the state equation and arbitrary functions of the integrals. The equivalent transformations were found for arbitrary element. The problem of the group classification was solved when admitted algebra was expanded for 8 cases of arbitrary element. The optimal systems of dissimilar subalgebras were obtained for the Lie algebras from the group classification. The example of the invariant vortex motion from the point source or sink was done. The regular partial invariant submodel was considered for the 2-dimensional subalgebra. It describes the turn of a vortex flow in the strip and on the plane with asymptotes for the stream line.

First results of a promising Doppler lidar configuration to derive wind gusts within the FESSTVaL campaign

<p>A central aspect of the Field Experiment on Sub-Mesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL, www.fesstval.de) is the investigation of wind gusts with Doppler lidar measurements. Compared to meteorological tower observations, they have the advantage of being able to probe higher altitudes of the atmosphere, they thus offer the possibility to record a vertical profile of wind gusts with a resolution of about 30 m in the atmospheric boundary layer. Nevertheless, it is difficult to capture wind gusts with these instruments as it is challenging to measure fluctuations of short duration with an instrument which needs a certain time for one complete measurement.</p><p>Based on the research of Suomi et al. (2017), different configurations were tested in a pre-campaign in autumn 2019 to identify a suitable measurement mode for Halo Photonics Stream Line Scanning Doppler LiDAR systems. Different lidars were operated in parallel to compare configurations against each other. A promising mode was tested during the FESST@MOL campaign in summer 2020 for a three month period. This is a continous scan mode (CSM) configuration that takes about 3.4 seconds per circulation and performs measurements in 10-11 directions.</p><p>The derived wind gusts and mean wind speeds are compared with high resolution sonic anemometer measurements at 90.3 m to verify the quality of the lidar measurements. In a first comparison good agreement is shown despite the different measuring principles. In addition, various parameters are tested to identify optimal thresholds that allow a reliable derivation of wind gusts.</p><p>In summer 2021 this fast CSM mode will be operated and further tested in the FESSTVaL campaign in parallel with UAS measurements. Moreover lidars will be installed at different locations to analyse the spatial characteristics of wind gusts with this scanning configuration.</p><p><strong>Reference</strong></p><p>Suomi, I., Gryning, S.‐E., O'Connor, E.J. and Vihma, T. (2017), Methodology for obtaining wind gusts using Doppler lidar. Q.J.R. Meteorol. Soc., 143: 2061-2072. https://doi.org/10.1002/qj.3059</p>

Numerical Investigation of Newtonian Fluid Flow around Sharp & Rounded Corner Rectangular Obstruction

In the present study, very stable and converging Least Square finite element method (LSFEM) is employed to calculate the approximate solution of steady state Navier – Stokes equation, consisting continuity and momentum equations in two dimensions. The 2D rectangular domain is considered to study the behavior of linear fluid passing two parallel rectangular obstructions in an open channel. The current numerical analysis is based on two instances, in the first one two rectangular obstructions possesses sharp corners set to face the entering flow while in the other case, obstructions having round corners are analyzed concerning to examine the enhancement in the size of vortex formed due to the flow blockage, intensity of vortex and the recirculation flow rate in the dead zone for Reynolds number from 250 to 2000. The stream line patterns are also presented to monitor the changes appears in the shape of vortex for different Re. The information gather through the analysis suggests the cutoff corner obstruction is congenial in restricting the vortex length and favorable for slow down the flow circulation rate in the lower stream of the channel. The acquired results are compared with established data in past literature which turn out to be in good agreement.

Typhonium phuocbinhense sp. nov. (Araceae: Areae), a new species from central Vietnam

Typhonium phuocbinhense has been described as a new species from central Vietnam. The plant grows on sand-soil in the gaps of rocks and the banks of stream line in the Phuoc Binh National Park of Ninh Thuan Province. The species is different from all other species in the genus. It is closest to T. varians from Thailand but differs from this species by having leaves not variegated, spathe tube brown and spathe lamina much narrower and staminodes folded 180o at apex. Beside that the species key of Typhonium in Vietnam and the species information of distribution, ecology, habitat and conservation are also introduced.

Hydromagnetic Flow of Prandtl Nanofluid Past Cylindrical Surface with Chemical Reaction and Convective Heat Transfer Aspects

Thermodynamical attributes of non-Newtonian fluids over stretched surfaces have gained pervasive essence due to extensive utilization in extruding plastic sheet procedures, liquid film condensation, glass blowing, paper production, biopolymer cylinder coatings, and so forth. So, currently communication is aimed to candidly explicate flow characteristic of Prandtl fluid generated by axial stretching of cylindrical surface. Mathematical modelling by using conservation laws of momentum, energy and concentration fields containing the aspects of magnetic field, convective heating, and chemical reaction are presented initially in the form of partial differential expressions. Later on, these attained PDEs are transmuted into nonlinear ordinary differential equations with implementation of similarity variables. Numerical approach renowned as shooting technique with improved coefficient of the Runge–Kutta (R–K) method by Cash and Karp is used to access accurate solution. Linear curved fitting analysis is also performed to analyze results. Influence of flow-controlling parameters on associated profiles is revealed through graphical visualization. Stream line plots representing flow behavior of Prandtl fluid versus different magnitudes of the curvature parameter are adorned. Variation in friction drag force at wall, heat flux, and concentration gradient are evaluated through numerical data and with interpolation of linear curved fittings. It is deduced from results that increasing curvature parameter momentum and temperature distributions enriches whereas skin-friction coefficient depicts reverse pattern. It is also inferred that temperature shows incrementing deviation in the absence of chemical reaction whereas concentration profiles exhibit reduction with consideration of influence of chemical reaction parameter. Magnetic field tends to reduce the velocity and create thinness of boundary layer thickness.

Heat and mass transfer effects of peristaltic motion of a Jeffery fluid in a tube

The impact of heat and mass transfer were analyzed in the present investigation by considering the peristaltic transport of a Jeffery fluid with nanoparticles in a uniform tube. Lubrication theory hypotheses have been considered and expressions have been defined for axial velocity, pressure drop, frictional force, heat and mass transfer effects. The patterns of the stream line and trapped bolus were graphically depicted at the end. It is found that with regard to the modification of various parameters, pressure drop and frictional force exhibit identical behavior. By increasing/decreasing the local temperature Grashof number, Brownian motion parameter and local nanoparticle Grashof number, pressure drop and axial velocity can be regulated.

Mixing Performance of Inner Baffle in Shear Thinning Fluid

A mixing performance of an inner baffle was investigated in shear thinning fluid. The inner baffle was placed with a clearance between baffle and vessel wall. A traditional two-bladed paddle impeller was used. Four planar baffles were vertically placed in two ways: 1) standard baffle condition 2) inner baffle condition. The standard baffle condition was that the baffle was placed on the mixing vessel wall. A mixing pattern was visualized by decolorization method based on an oxidation-reduction reaction with sodium thiosulfate and iodine. Flow field for shear thinning fluid in mixing vessel was measured by particle image velocimetry and was shown as stream line. A pair of isolated mixing regions (IMR) like doughnut-ring formed above and below the impeller under standard baffle condition. However, IMR dissipated under inner baffle condition. As a result, a mixing time under the inner baffle condition was drastically decreased. This study suggested that inner baffle promoted mixing in shear thinning fluid.