Numerical Simulation of Room Airflow Using Different Closure Models and Grid Generation Schemes

2002 ◽  
Author(s):  
Anupreet Singh ◽  
Mohammad H. Hosni ◽  
Walter R. Schwarz
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Cross Sections ◽  
Heat Rate ◽  
Grid Generation ◽  
Computer Hardware ◽  
Experimental Investigations ◽  
Human Thermal Comfort ◽  
Closure Models ◽  
Technological Advances

Proper distribution of conditioned air plays an important role in both human thermal comfort and indoor air quality. Experimental investigations of airflow and temperature distributions for typical indoor environmental conditions are essential but expensive and time consuming. Technological advances in computer hardware and development of computational software in recent years have made numerical simulations of such flow conditions possible. The objectives of this study were to: (1) Evaluate the applicability of a commercial software in conducting numerical simulations of indoor airflow conditions for both isothermal and non-isothermal conditions using different turbulence closure models, and (2) Determine the effects of different grid generation techniques on the numerical results. The computations were performed for a large rectangular geometry room. Conditioned air entered the room through a high sidewall grille located on one side of the wall and exited through a return located on the opposite side of wall. All walls and ceiling were insulated. The floor was heated at a constant heat rate. This paper presents velocity, temperature, and turbulent kinetic energy profiles at various cross-sections. Good agreements between the numerical simulation results and experimental data were achieved.

scholarly journals Optimal Design Methodology of Tapered Waveguide Transducers for Thickness Monitoring

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1892
Author(s):  
Jiuhong Jia ◽  
Yue Ren ◽  
Weiming Wang ◽  
Zuoyu Liao ◽  
Xiancheng Zhang ◽  
...  
Keyword(s):  
High Temperature ◽  
Optimal Design ◽  
Numerical Simulations ◽  
Cross Sections ◽  
Design Methodology ◽  
Wave Attenuation ◽  
Experimental Investigations ◽  
Tapered Waveguide ◽  
Solid Foundation ◽  
Shear Horizontal

For the purpose of providing transducers for long-term monitoring of wall thinning of critical pressure equipment in corrosion or high temperature environments, the optimal design methodology for tapered waveguide units was proposed in the present study. Firstly, the feasibility of the quasi-fundamental shear horizontal (SH0*) wave propagating in the tapered waveguide units was analyzed via numerical simulations, and the transmitting limitations of the non-dispersive SH0* wave were researched. Secondly, several tapered waveguide transducers with varying cross-sections to transmit pure SH0* wave were designed according to the numerical results. Experimental investigations were carried out, and the results were compared with waveguide transducers with a prismatic cross-section. It was found that the tapered waveguide units can transmit non-dispersive shear horizontal waves and suppress the wave attenuation at the same time. The experimental results agreed very well with the numerical simulations. Finally, high-temperature experiments were carried out, and the reliability of thickness measuring by the tapered waveguide transducers was validated. The errors between the measured and the true thicknesses were small. This work paves a solid foundation for the optimal design of tapered waveguide transducers for thickness monitoring of equipment in harsh environments.

scholarly journals Influence of application of Hottel’s zonal model and six-flux model of thermal radiation on numerical simulations results of pulverized coal fired furnace

2012 ◽  
Vol 16 (1) ◽  
pp. 271-282 ◽  
Author(s):  
Nenad Crnomarkovic ◽  
Miroslav Sijercic ◽  
Srdjan Belosevic ◽  
Dragan Tucakovic ◽  
Titoslav Zivanovic
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Gas Phase ◽  
Computation Time ◽  
Heat Rate ◽  
Furnace Operation ◽  
Pulverized Coal ◽  
Zonal Model ◽  
Flux Model ◽  
Phase Temperature

Difference of results of numerical simulation of pulverized coal fired furnace when mathematical models contain various radiation models has been described in paper. Two sets of numerical simulations of pulverized coal fired furnace of 210 MWe power boiler have been performed. One numerical simulation has contained Hottel?s zonal model, whereas the other numerical simulation has contained six-flux model. Other details of numerical simulations have been identical. The influence of radiation models has been examined through comparison of selected variables (gas-phase temperature, oxygen concentration, and absorbed radiative heat rate of surface zones of rear and right furnace walls), selected global parameters of furnace operation (total absorbed heat rate by all furnace walls and furnace exit gas-phase temperature). Computation time has been compared as well. Spatially distributed variables have been compared through maximal local differences and mean differences. Maximal local difference of gas-phase temperature has been 8.44%. Maximal local difference of absorbed radiative heat rate of the surface zones has been almost 80.0%. Difference of global parameters of furnace operation has been expressed in percents of value obtained by mathematical model containing Hottel?s zonal model and has not been bigger than 7.0%. Computation time for calculation of 1000 iterations has been approximately the same. Comparison with other radiation models is necessary for assessment of differences.

scholarly journals Wind shear over the Nice Côte d'Azur airport: case studies

2013 ◽  
Vol 13 (9) ◽  
pp. 2223-2238 ◽  
Author(s):  
A. Boilley ◽  
J.-F. Mahfouf
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Numerical Simulations ◽  
Wind Shear ◽  
Horizontal Wind ◽  
Wind Profiler ◽  
Measurement Campaign ◽  
Wind Lidar ◽  
Real Time Applications ◽  
Wind Shears

Abstract. The Nice Côte d'Azur international airport is subject to horizontal low-level wind shears. Detecting and predicting these hazards is a major concern for aircraft security. A measurement campaign took place over the Nice airport in 2009 including 4 anemometers, 1 wind lidar and 1 wind profiler. Two wind shear events were observed during this measurement campaign. Numerical simulations were carried out with Meso-NH in a configuration compatible with near-real time applications to determine the ability of the numerical model to predict these events and to study the meteorological situations generating an horizontal wind shear. A comparison between numerical simulation and the observation dataset is conducted in this paper.

Stefan Number-Insensitive Numerical Simulation of the Enthalpy Method for Stefan Problems Using the Space-Time Conservation Element and Solution Element Method

2004 ◽  
Author(s):  
Anahita Ayasoufi ◽  
Theo G. Keith ◽  
Ramin K. Rahmani
Keyword(s):  
Numerical Simulation ◽  
Phase Change ◽  
Numerical Simulations ◽  
Latent Heat ◽  
Space Time ◽  
Enthalpy Method ◽  
Stefan Problems ◽  
Stefan Number ◽  
Original Scheme ◽  
Solution Element

An improvement is introduced to the conservation element and solution element (CE/SE) phase change scheme presented previously. The improvement addresses a well known weakness in numerical simulations of the enthalpy method when the Stefan number, (the ratio of sensible to latent heat) is small (less than 0.1). Behavior of the improved scheme, at the limit of small Stefan numbers, is studied and compared with that of the original scheme. It is shown that high dissipative errors, associated with small Stefan numbers, do not occur using the new scheme.

Pneumatic pulsator design as an example of numerical simulations in engineering applications

2012 ◽  
Vol 2 (1) ◽  
Author(s):  
Krzysztof Wołosz ◽  
Jacek Wernik
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Cast Iron ◽  
Numerical Simulations ◽  
Stress Analysis ◽  
Aluminium Alloy ◽  
Loose Material ◽  
Engineering Applications ◽  
Pressure Losses ◽  
Pneumatic Impact

AbstractThe paper presents the part of the investigation that has been carried out in order to develop the pneumatic pulsator which is to be employed as an unblocking device at lose material silo outlets. The part of numerical simulation is reported. The fluid dynamics issues have been outlined which are present during supersonic airflow thought the head of the pulsator. These issues describe the pneumatic impact phenomenon onto the loose material bed present in the silo to which walls the pulsator is assembled. The investigation presented in the paper are industrial applicable and the result is the working prototype of the industrial pneumatic pulsator. The numerical simulation has led to change the piston shape which is moving inside the head of the pulsator, and therefore, to reduce the pressure losses during the airflow. A stress analysis of the pulsator controller body has been carried out while the numerical simulation investigation part of the whole project. The analysis has made possible the change of the controller body material from cast iron to aluminium alloy.

Numerical simulation of squeezing Cu–Water nanofluid flow by a kernel-based method

2021 ◽  
pp. 2250005
Author(s):  
Mojtaba Fardi ◽  
Yasir Khan
Keyword(s):  
Numerical Simulation ◽  
Hilbert Space ◽  
Linear System ◽  
Numerical Simulations ◽  
Numerical Results ◽  
Kernel Matrix ◽  
Nanofluid Flow ◽  
Parallel Disks ◽  
Engineering Problems ◽  
Well Conditioning

The main aim of this paper is to propose a kernel-based method for solving the problem of squeezing Cu–Water nanofluid flow between parallel disks. Our method is based on Gaussian Hilbert–Schmidt SVD (HS-SVD), which gives an alternate basis for the data-dependent subspace of “native” Hilbert space without ever forming kernel matrix. The well-conditioning linear system is one of the critical advantages of using the alternate basis obtained from HS-SVD. Numerical simulations are performed to illustrate the efficiency and applicability of the proposed method in the sense of accuracy. Numerical results obtained by the proposed method are assessed by comparing available results in references. The results demonstrate that the proposed method can be recommended as a good option to study the squeezing nanofluid flow in engineering problems.

Numerical Modeling of Multi-Frequency Complex Dielectric Permittivity Dispersion of Sedimentary Rocks

Geophysics ◽  
2021 ◽  
pp. 1-69
Author(s):  
Artur Posenato Garcia ◽  
Zoya Heidari
Keyword(s):  
Numerical Simulation ◽  
Dielectric Permittivity ◽  
Numerical Simulations ◽  
Dielectric Response ◽  
Water Saturation ◽  
Pore Scale ◽  
Simulation Results ◽  
Wet Rocks ◽  
Permittivity Measurements ◽  
The Impact

The dielectric response of rocks results from electric double layer (EDL), Maxwell-Wagner (MW), and dipolar polarizations. The EDL polarization is a function of solid-fluid interfaces, pore water, and pore geometry. MW and dipolar polarizations are functions of charge accumulation at the interface between materials with contrasting impedances and the volumetric concentration of its constituents, respectively. However, conventional interpretation of dielectric measurements only accounts for volumetric concentrations of rock components and their permittivities, not interfacial properties such as wettability. Numerical simulations of dielectric response of rocks provides an ideal framework to quantify the impact of wettability and water saturation ( Sw) on electric polarization mechanisms. Therefore, in this paper we introduce a numerical simulation method to compute pore-scale dielectric dispersion effects in the interval from 100 Hz to 1 GHz including impacts of pore structure, Sw, and wettability on permittivity measurements. We solve the quasi-electrostatic Maxwell's equations in three-dimensional (3D) pore-scale rock images in the frequency domain using the finite volume method. Then, we verify simulation results for a spherical material by comparing with the corresponding analytical solution. Additionally, we introduce a technique to incorporate α-polarization to the simulation and we verify it by comparing pore-scale simulation results to experimental measurements on a Berea sandstone sample. Finally, we quantify the impact of Sw and wettability on broadband dielectric permittivity measurements through pore-scale numerical simulations. The numerical simulation results show that mixed-wet rocks are more sensitive than water-wet rocks to changes in Sw at sub-MHz frequencies. Furthermore, permittivity and conductivity of mixed-wet rocks have weaker and stronger dispersive behaviors, respectively, when compared to water-wet rocks. Finally, numerical simulations indicate that conductivity of mixed-wet rocks can vary by three orders of magnitude from 100 Hz to 1 GHz. Therefore, Archie’s equation calibrated at the wrong frequency could lead to water saturation errors of 73%.

scholarly journals Numerical Simulations of V-Shaped Plates Subjected to Blast Loadings: A Validation Study

2016 ◽  
Vol 10 (11) ◽  
pp. 203
Author(s):  
Mohd Zaid Othman ◽  
Qasim H. Shah ◽  
Muhammad Akram Muhammad Khan ◽  
Tan Kean Sheng ◽  
M. A. Yahaya ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Variable Mass ◽  
Blast Loading ◽  
Experimental Results ◽  
Average Difference ◽  
Simulation Results ◽  
Blast Loadings ◽  
Carrier Vehicle ◽  
Good Agreement

A series of numerical simulations utilizing LS-DYNA was performed to determine the mid-point deformations of V-shaped plates due to blast loading. The numerical simulation results were then compared with experimental results from published literature. The V-shaped plate is made of DOMEX 700 and is used underneath an armour personal carrier vehicle as an anti-tank mine to mitigate the effects of explosion from landmines in a battlefield. The performed numerical simulations of blast loading of V-shaped plates consisted of various angles i.e. 60°, 90°, 120°, 150° and 180°; variable mass of explosives located at the central mid-point of the V-shaped vertex with various stand-off distances. It could be seen that the numerical simulations produced good agreement with the experimental results where the average difference was about 26.6%.

Problems of Cold-Bent Notched C-Shaped Profile Members

2014 ◽  
Vol 941-944 ◽  
pp. 1871-1875 ◽  
Author(s):  
Nikolay I. Vatin ◽  
Tatiana Nazmeeva ◽  
Roman Guslinscky
Keyword(s):  
Bearing Capacity ◽  
Cross Sections ◽  
Experimental Investigations ◽  
Heat Current ◽  
Thermal Profile ◽  
Engineering Structures ◽  
Normative Documents ◽  
Steel Members ◽  
Global Buckling ◽  
Stability Of Structures

Nowadays cold bent steel thermal сold-bent С-profile is widely used in building construction but we still have some little studied questions in the fields of thermal conductivity, air permeability, resistibility and corrosion behavior of the profile. Cold-bent notched С-profile is used for interior exterior panel members. Lengthwise notches made chequerwise in the profile walls increase the distance of heat flow and decrease heat conductivity and eliminate cold bridges that is why the profile is called “thermal profile”. Cold-bent profile made by cold bending requires alternate approach when engineering structures are designed and maintained. The approach means thin walls’ and the profile special form’ impact on the bearing capacity and stability of the structures should be taken into account. In spite of the wide use of cold-bent notched C-profile in building frameworks, we see lack of information on how the notches influence the bearing capacity and stability of structures. There are no official normative documents on calculation and designing of cold-bent notched profile structures. We carry out theoretical and experimental investigations on global buckling and bearing capacity of steel members of C-shaped notched profiles of different cross-sections area. We carry out theoretical and experimental investigations on heat current passing through the thermal profile structure is held with the use of testing bed.

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