scispace - formally typeset
Search or ask a question
Author

Abdolamir Bak Khoshnevis

Bio: Abdolamir Bak Khoshnevis is an academic researcher from Hakim Sabzevari University. The author has contributed to research in topics: Turbulence & Curvature. The author has an hindex of 7, co-authored 22 publications receiving 133 citations.

Papers
More filters
Journal ArticleDOI
15 Sep 2016-Energy
TL;DR: In this article, a comprehensive thermo-economic analysis was accomplished on several CGSs of Iran to find the most optimal combined heat and power (CHP) system size and design for each station and define a general criterion by which one could realize that if a CGS can efficiently employ CHP technology Net present value (NPV) approach is used to analyze and compare the performance of these stations economically.

38 citations

Journal ArticleDOI
TL;DR: In this paper, three popular offshore wind turbine airfoil geometries (S822, S825, and SD7062) are studied in terms of entropy generation.

26 citations

Journal ArticleDOI
TL;DR: In this paper, the entropy generation rate is considered as a criterion in the analysis of this mechanism and also a tool for accurate designing, which could be a strong tool to design accurate and offshore wind turbines with lower losses in near future.

24 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the effect of changing geometric parameters according to the presence of wetness in the flow field, such as the length and diameter of the constant area section of the ejector and the diameter of primary nozzle throat.
Abstract: In this research, the improvement of an ejector performance has been studied as crucial part of an ejector refrigeration system by means of applying changes in its geometry. Water steam is taken as a non-expensive, non-toxic, and available refrigerant and wet steam model has been employed to more accurate numerical simulation and analysis. It is investigated the effect of changing geometric parameters according to the presence of wetness in the flow field. The geometric parameters are the length and diameter of the constant area section of the ejector and the diameter of primary nozzle throat. In addition to entrainment ratio (ER) and critical compression ratio (CR) of the ejector as conventional design criteria, COP of the refrigeration system and the total entropy generation (EG) in the flow inside the ejector are also used; which results in a novel EEC ( E ntropy generation, E ntrainment ratio, and C oefficient of performance) method for ejector design in the ejector refrigeration systems. The impact of changing each geometry parameter is examined in a separate process. Finally, the increment in the length and diameter of the constant area section and decrement in the diameter of the primary nozzle throat are considered as desirable changes. Consequently, by applying these changes ER and COP have improved by 32% and total entropy generation is decreased.

24 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of adverse pressure gradient and of curvature on the wake-boundary-layer interaction are studied separately and in combination, and the effect of curvatures is to make the wake asymmetric.
Abstract: Measurements of mean velocity and turbulent quantities have been carried out when the wake of a symmetrical airfoil interacts with the boundary layer on the (i) walls of a straight duct/diffuser and (ii) convex and concave walls of a curved duct/diffuser. The effects of adverse pressure gradient and of curvatures on the interaction are studied separately and in combination. Six cases are considered, viz. with (i) neither pressure gradient nor curvature, (ii) adverse pressure gradient and no curvature, (iii) and (iv) convex curvature with zero and adverse pressure gradients, respectively, (v) and (vi) concave curvature with zero and adverse pressure gradients, respectively. For the flows with curvature, the curvature parameter δ/R is 0.023, and for the flows with adverse pressure gradient, the Clauser pressure gradient parameter β is 0.62. The individual influences of adverse pressure gradient and convex and concave curvatures on the boundary layer are similar to those observed by earlier investigations. It is further observed that the combined effect of concave/convex curvature and the adverse pressure gradient causes higher turbulence intensities than the sum of the individual effects. The effect of curvature is to make the wake asymmetric, and in combination with adverse pressure gradient the asymmetry increases. It is observed that the adverse pressure gradient causes faster wake–boundary-layer interaction. Comparing measurements in a straight duct, a curved duct, a curved diffuser and a straight diffuser, it is seen that the convex curvature reduces the boundary layer thickness. The asymmetry in wake development compensates for this effect and the wake–boundary-layer interaction on a convex surface is almost the same as that on a straight surface. In the case of interaction with the boundary layer on a concave surface, the curvature increases the boundary layer thickness and causes enhanced turbulence intensities. However, the asymmetry in wake is such that the extent of wake is lower towards the boundary layer side. As a result, the wake–boundary-layer interaction on concave surface is almost the same as on a straight surface. The interaction is faster in the presence of adverse pressure gradient.

15 citations


Cited by
More filters
Book ChapterDOI
01 Jan 1997
TL;DR: The boundary layer equations for plane, incompressible, and steady flow are described in this paper, where the boundary layer equation for plane incompressibility is defined in terms of boundary layers.
Abstract: The boundary layer equations for plane, incompressible, and steady flow are $$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

2,598 citations

Journal ArticleDOI
TL;DR: In this paper, the authors highlight some of the most recent advances in greenhouse technology and CEA in order to raise the awareness for technology transfer and adaptation, which is necessary for a successful transition to urban agriculture.
Abstract: Greenhouse cultivation has evolved from simple covered rows of open-fields crops to highly sophisticated controlled environment agriculture (CEA) facilities that projected the image of plant factories for urban agriculture The advances and improvements in CEA have promoted the scientific solutions for the efficient production of plants in populated cities and multi-story buildings Successful deployment of CEA for urban agriculture requires many components and subsystems, as well as the understanding of the external influencing factors that should be systematically considered and integrated This review is an attempt to highlight some of the most recent advances in greenhouse technology and CEA in order to raise the awareness for technology transfer and adaptation, which is necessary for a successful transition to urban agriculture This study reviewed several aspects of a high-tech CEA system including improvements in the frame and covering materials, environment perception and data sharing, and advanced microclimate control and energy optimization models This research highlighted urban agriculture and its derivatives, including vertical farming, rooftop greenhouses and plant factories which are the extensions of CEA and have emerged as a response to the growing population, environmental degradation, and urbanization that are threatening food security Finally, several opportunities and challenges have been identified in implementing the integrated CEA and vertical farming for urban agriculture Keywords: smart agriculture, greenhouse modelling, urban agriculture, vertical farming, automation, internet of things (IoT), wireless sensor network, plant factories DOI: 1025165/jijabe201811013210 Citation: Shamshiri R R, Kalantari F, Ting K C, Thorp K R, Hameed I A, Weltzien C, et al Advances in greenhouse automation and controlled environment agriculture: A transition to plant factories and urban agriculture Int J Agric & Biol Eng, 2018; 11(1): 1–22

247 citations

Journal ArticleDOI
TL;DR: In this article, high-resolution laser-Doppler anemometer measurements were acquired in a two-dimensional turbulent boundary layer over a ramp, where the boundary layer is then subjected to a varying pressure gradient along the length of the ramp and partially redevelops on a downstream flat plate.
Abstract: High-resolution laser-Doppler anemometer measurements were acquired in a two-dimensional turbulent boundary layer over a ramp. The goals were to provide a detailed data set for an adverse pressure gradient boundary layer far from separation and to examine near-wall behaviour of the Reynolds stresses as compared to flat-plate boundary layers. The flow develops over a flat plate, reaching a momentum thickness Reynolds number of 3350 at an upstream reference location. The boundary layer is then subjected to a varying pressure gradient along the length of the ramp and partially redevelops on a downstream flat plate. Mean velocity measurements show a log law region in all velocity profiles, but the outer layer does not collapse in deficit coordinates indicating that the boundary layer is not in equilibrium. Measurements of non-dimensional stress ratios and quadrant analysis of the two-component data indicate relatively small changes to the turbulence structure. However, the streamwise normal stress has an extended outer layer plateau, and the shear stress and wall-normal stress have outer layer peaks. Near the wall, the streamwise normal stress and shear stress collapse with flat-plate data using standard scaling, but the wall normal stress is substantially larger than flat-plate cases.

79 citations

Journal ArticleDOI
TL;DR: In this article, the feasibility of using the air source heat pump (ASHP), as a waste heat recovery system operating with different refrigerants, in a 54-racks data center in Mashhad city of Iran has been investigated to save the electrical energy consumption of the mechanical cooling as well as the natural gas fuel consumption of an adjoining office building with area of 416m2.

77 citations

Journal Article
TL;DR: In this article, statistically steady turbulent flow in straight and curved pipes at moderate Reynolds numbers is studied in detail using direct numerical simulations (DNS) based on a spectral elem.
Abstract: Fully developed, statistically steady turbulent flow in straight and curved pipes at moderate Reynolds numbers is studied in detail using direct numerical simulations (DNS) based on a spectral elem ...

71 citations