Abdorrasoul Mayyahi; Aghil Yousefikoma; Ali Rangin Kaman; Hesam Maleki
Abstract
An autonomous underwater vehicle (AUV) with less noise and vortices as well as efficient power consumption, is pursued in this research by inspiration of shark swimming. Design, hydrodynamic analysis, modeling, fabrication, navigation, and control of this novel AUV is the main goal of this research. ...
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An autonomous underwater vehicle (AUV) with less noise and vortices as well as efficient power consumption, is pursued in this research by inspiration of shark swimming. Design, hydrodynamic analysis, modeling, fabrication, navigation, and control of this novel AUV is the main goal of this research. Detailed explanation of the test and experiment with a brief overview on fabrication are provided. The transfer function of the system has been extracted from the experimental data. The transfer function is then employed for dynamic analysis and control system development. Zigler-Nickols method is used to predetermine the PID control coefficients. Consequently, small modifications have been done by trial and error. Trajectory control in a 10 cm off the wall and in a 20 cm band in a large swimming pool has been examined by a 3 DOF AUV.
Hooman Naimi; Mehrdad Raisee
Abstract
The present paper deals with the prediction of three-dimensional fluid flow and heat transfer in rib-roughened ducts of square cross-section. Such flows are of direct relevance to the internal cooling system of modern gas turbine blades. The main objective is to assess how a recently developed variant ...
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The present paper deals with the prediction of three-dimensional fluid flow and heat transfer in rib-roughened ducts of square cross-section. Such flows are of direct relevance to the internal cooling system of modern gas turbine blades. The main objective is to assess how a recently developed variant of a cubic non-linear model (proposed by Craft et al. (1999)), that has been shown to produce reliable thermal predictions through axi-symmetric and plane two-dimensional ribbed passages (Raisee et al. (2004)), can predict flow and heat transfer characteristics through more complex three-dimensional ribbed ducts. To fulfil this objective, the present paper discusses turbulent air flow and heat transfer through two different configurations, namely: (I) a square duct with “in-line” ribs normal to the flow direction at and (II) a square duct with normal ribs in a “staggered” arrangement at . In this paper the flow and thermal predictions of the linear model (EVM) are also included, as a set of baseline predictions. Both turbulence models have been used with the form of length-scale correction term to the dissipation rate originally proposed by ‘Yap’ and also a differential version of this term, ‘NYP’. The mean flow predictions show that both linear and non-linear models can successfully reproduce most of the measured data for stream-wise and cross-stream velocity components. Moreover, the non-linear model, which is sensitive to turbulence anisotropy, is able to produce better results for the turbulent stresses. As far as heat transfer predictions are concerned, it was found that both EVM and NLEVM2, the more recent variant of the non-linear , with the algebraic length-scale correction term, overestimate the measured Nusselt numbers for both geometries examined. While the EVM with the differential length-scale correction term underestimates heat transfer levels, the Nusselt number predictions with the NLEVM2 and the ‘NYP’ term are in close agreements with the measured data. Comparisons with our earlier work, Iacovides and Raisee (1999), show that the NLEVM2 thermal predictions are of similar quality to those of a second-moment closure. This modified version of the non-linear model, that in earlier studies was shown to improve thermal predictions in axi-symmetric and plane ribbed passages, is thus now found to also produce reasonable heat transfer predictions in three-dimensional ribbed ducts.
Sara Farhangi; Mojtaba Shariati Niasar; Mohammad Soltanieh; Mehdi Pourafshari Chenar
Abstract
It is several decades that the application of membrane processes for gas separation has become a great concern within industries. Among them, the polymeric membranes of different structures have played the most important role. Such application has been widely extended to gas separation and due to the ...
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It is several decades that the application of membrane processes for gas separation has become a great concern within industries. Among them, the polymeric membranes of different structures have played the most important role. Such application has been widely extended to gas separation and due to the necessity of both; prediction of the behavior of these processes and recognition of the effective parameters on membrane processes, in this research a mathematical model of mass transfer through polymeric asymmetric membranes is presented. Within the dense section of the membrane, a dual sorption model is applied, while for the porous section, the average effect of the four flow mechanisms; namely Knudsen, viscous, slip as well as surface flow are implemented. Basing on the experimental values of gas permeances through different membranes and by using a proper optimization method, the available membrane transport parameters were determined.
Ahmad Darabi; Hamid Lesani; Teymour Ghanbari Hashemabadi
