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Background: Obesity and its complications are global health concerns with rising interests, and in Bangladesh, the scenario is not different. This study was designed to analyze the effect of BMI on postoperative outcomes in patients who underwent Off-Pump Coronary Artery Bypass (OPCAB)graft surgery. Methods: This prospective observational study was conducted from September 2017 to August 2018 in the department of cardiac surgery, NICVD & 90 patients were divided into two groups. 43 patients in group A, with BMI ≥ 25 kg/m2 and 47 patients in group B, with BMI

The swirling blood flow in cardiovascular system has both beneficial and detrimental effects on hemodynamic parameters. A numerical investigation has been performed in a model stenosed artery to analyse the effects of swirling in non-Newtonian pulsatile blood flow through arterial stenosis. The standard k-ω turbulent model is used for the simulation of pulsatile blood flow with swirling. In this investigation, the Reynolds number varies from 200 to 1000. The wall shear stress, hydrostatic pressure and centreline velocity patterns at different time steps are obtained to compare the swirling effect with no swirl condition. Wall shear stress and hydrostatic pressure are not affected by swirling. The streamline contours show that swirling causes substantial variation in velocity distribution. The massive turbulence near the wall is observed in post stenotic region as a dominant effect of swirling. The effect of pulsatile swirl flow is discussed with the relevant pathological conditions.

Fuel crisis is a major problem for airline industry. Operating cost of this industry will eventually be increased with the increase of fuel crisis. So, it is necessary to design more fuel efficient aircraft. Reducing aerodynamic drag is a great way to minimize fuel consumption. Two thirds of aircraft drag are produced from the wings. This drag is a combination of profile drag, induced drag and compressibility drag. The drag breakdown of a typical transport aircraft shows that the induced drag can be as much as 40% of the total drag at cruise conditions and 80–90% of the total drag in take-off configuration. Hence, reducing induced drag is a great way to save fuel cost during takeoff and results in a longer cruising range. This study deals with the curved trailing edge tapered wing by adding different winglets at the wing tip. All the models are tested at air speed of 98.64 km/h (0.08 Mach). The Static pressure at different AOA (-4°, 0°, 4°, 8°, 12°, 16°, 20° & 24°) is measured from both upper and lower surfaces of the wing models through different pressure tapping by using a multi-tube water manometer. The aerodynamic characteristics (Coefficient of Lift, Coefficient of Drag and Lift to Drag ratio) for different models are determined from the static pressure distribution. The experimental results show that lift to drag ratio increases and induced drag decreases for wing models with winglets compared to wing model without winglet for the Reynolds number considered in the present study.

The present numerical study has been conducted to explore on the effects of external magnetic field at different angle of inclination on the flow driven by the combined mechanism of buoyancy and thermo-capillary flow in an open enclosure. The enclosure is provided with localized heating from below and symmetric cooling is assumed from sides. Along the free surface on the top of the enclosure, the surface tension varies with temperature difference which is known as the Marangoni effect and also called the thermo-capillary effect. The governing equation of the system (i.e. mass, momentum and energy) are presented in the non-dimensional form along with necessary boundary conditions and hence been solved numerically by Galerkin finite element method (FEM) with triangular discretization system. The effect of pertinent parameters such as Hartmann number (0 < Ha < 100), angle of inclination of the magnetic field (0° < ϕ < 90°), Grashof number (103 < Gr < 106), Marangoni number (-100 < Ma < 100) and Prandtl number (0.7 < Pr < 7) on the isotherms, streamlines inside the enclosure as well the heat transfer performance of the system have been explored for various parametric conditions of the system. One key observation is flow field changes drastically with angle of inclination in the presence of the Marangoni effect. And also the heat transfer increases at higher Prandtl number and Grashof number.

This paper reports on the experimental investigation of the aerodynamic effects on even and odd number bladed vertical axis vane type rotor. The experiment was conducted with the help of a subsonic wind tunnel together with the experimental set-up of the vane type rotor and a spring balance. To ensure a Reynolds number independent approach, different stream flow was maintained. The flow velocities varied from 5 m/s to 9 m/s covering the Reynolds number from 0.6375 X 10^5 to 1.2 X 10^5. A four, five and six bladed vertical axis vane typerotor was used to determine the aerodynamic properties in dynamic condition. It is found that the power coefficient increases with increasing the number of blade but the significant effect of even and odd number blade is observed on the range of tip speed ratio. An odd number bladed rotor covered a wide range of tip speed ratio compare to the even number one.

In the present study, an investigation has been carried out for the unsteady turbulent flow over two side-by-side rotating circular cylinders of the same diameter. Reynolds-Average Navier-Stokes (RANS) equations along with SST (Shear Stress Transport) model are solved using finite element method in order to study the characteristics of turbulent flow. Linear triangular mesh elements are used for the grid generation of the computational domain. These grids are employed for both velocity and pressure interpolation at different points of the domain. Simulation is performed at a high Reynolds number of Re = 10,000 based on the free stream velocity of the fluid, U∞ and the diameter of the cylinder, D. Besides, the spin ratio (α), which is defined as the ratio of the circumferential velocity (Uθ) and the free stream velocity of the fluid, is varied from 0 to 1. Another governing parameter, gap ratio (T/D) between the two cylinders is also varied from 2 to 4, where T is the transverse distance between the centers of the two cylinders. Influences of two different rotating combinations of the cylinders on the aerodynamic characteristics of the problem are also examined. In one combination, the upper cylinder rotates in the counterclockwise direction, while the lower cylinder rotates in clockwise direction and vice versa. In order to observe the aerodynamic performance of the present model, lift and drag coefficients are computed from the computational results. The wake region behind the rotating cylinders and the separation points over the cylinders are also observed.

Enhancement of heat removal and reduction of fin size become a major concern in designing heat exchanger equipment. The present paper reports an experimental analysis to investigate the turbulent heat transfer performance of rectangular fin arrays, both solid and circular perforations along the length of the fins. The size and number of circular perforation have been varied. Tests have been conducted in a horizontal wind tunnel equipped with forced draft fan. The data are obtained by varying flow velocities while maintaining constant heat input and taken over a period of time. The Reynolds number is varied between 6 × 10 4 through 25 × 10 4 . The heat loss due to radiation and convection is taken into account during calculation. Thermal performances and effectiveness of perforation and equivalent surface solid fin arrays have been evaluated and compared. Results show remarkable heat transfer enhancement, lower thermal resistances, pressure drop and higher efficiencies, effectiveness for perforated fins with increasing number of perforations in addition to the considerable reduction in weight in comparison with solid fin arrays.

In this research work, an experimental investigation of wind effect on hexagonal cylinder was carried out. The study was performed on the single cylinder. The test was conducted in an open circuit wind tunnel at a Reynolds number of 4.22 x 10 4 based on the face width of the cylinder across the flow direction in a uniform flow velocity of 13.5 m/s. The test was carried out at various angles of attack from 0° to 50° at a step of 10°. The surface static pressures at the different locations of the cylinder were measured with the help of inclined multi-manometers. The wind velocity was kept constant at 13.5 m/s. The pressure coefficients were calculated from the measured values of the surface static pressure distribution on the cylinder. Later the drag and lift coefficients were obtained from the pressure coefficients by the numerical integration method. The results will enable the engineers and architects to design buildings more efficiently. Since the results will be expressed in the non-dimensional form they may be applied for the prototype building.

In the present study, mixed convection heat transfer inside a square cavity filled with Cu-water nanofluid has been investigated numerically. The bottom wall of the cavity is maintained at a constant high temperature while the vertical sidewalls are assumed to be at a constant low temperature. The top wall of the cavity is insulated and moving at a constant velocity. Galerkin finite element method has been employed to solve the continuity, momentum and energy balance equations for the present problem. Analysis of thermal and flow fields inside the cavity has been analysed in terms of isotherms, streamlines and heatlines for a wide range of the Richardson number and solid volume fraction of the nanoparticle. Particular attention was paid to the case of pure mixed convection case with the Richardson No being equal to 1 for various combinations of natural convection and forced convection effects. The heat transfer performance of the system has been analysed in terms of average Nusselt number over the heated wall for various parameters. The present study shows that the distribution of streamline, isothermal lines and heatlines are very sensitive to Richardson number. The present study also shows that larger heat transfer rates can be achieved with nanofluid than the base fluid for all conditions.

In the present research work the dynamic conditions of Multi S-shaped bladed rotor at different Reynolds number have been identified. The investigation on wind loading and aerodynamic effects on the four, five and six bladed S-shaped vertical axis vane type rotor has been conducted with the help of an open circuit subsonic wind tunnel. For different bladed rotor the flow velocities were varied from 5m/s to 9m/s covering the Reynolds numbers up to 1.35 x 105. It was experiential that by increasing the number of blades of rotor to the optimum limit considering all significant factors and at the same time by increasing its Reynolds number, the power output can be increased to its maximum level Finally, the nature of predicted dynamic characteristics has been examined by comparing with the existing research works. DOI: http://dx.doi.org/10.3329/jme.v44i1.19501

In this research work, an experimental investigation of wind effect on pentagonal cylinders was carried out. The study was performed on the single cylinder in an open circuit wind tunnel at a Reynolds number of 4.22 x 104 based on the face width of the cylinder across the flow direction in a uniform flow velocity of 13.5 m/s. The test was carried out at various angles of attack from 0° to 63° at a step of 9°. The surface static pressures at the different locations of the cylinder were measured with the help of inclined multi-manometers. The wind velocity was kept constant at 13.5 m/s. The pressure coefficients were calculated from the measured values of the surface static pressure distribution on the cylinder. Later the drag and lift coefficients were obtained from the pressure coefficients by the numerical integration method. The results will enable the engineers and architects to design buildings more efficiently. Since the results will be expressed in the nondimensional form they may be applied for the prototype building. DOI: http://dx.doi.org/10.3329/jme.v44i1.19499

Bangladesh, a developing country of south-east Asia with large population has agricultural economy.About 59 percent cultivable land needs irrigation. During dry season and due to climate change, demand ofelectricity for electric power irrigation is increasing. Irrigation by electric power is cheaper than diesel pump.Due to severe shortage of electricity it is difficult to meet the demand. Harnessing solar power for irrigation is agood alternative to grid electricity. This paper deals with the design, technical and economic analysis of a lowcost 1 hp (746 W) small size dc photovoltaic water pumping system for irrigation. A buck converter is designedand constructed to improve the performance of the dc pump. All components of the system are procured locallyexcept the solar panels.DOI: http://dx.doi.org/10.3329/jme.v43i2.17833

Static torque and drag coefficients of a stationary Savonius rotor with circular arc blade profile havebeen investigated by measuring the pressure distribution on the blade surfaces for different rotor angles.Experiments have been performed at a Reynolds Number 1.8×105 with rotors having no overlap. Resultsindicate that static torque coefficients vary considerably with the rotor angle.DOI: http://dx.doi.org/10.3329/jme.v43i2.17830

An experimental investigation of surface static pressure distributions on octagonal cylinder in uniform and turbulent flows was carried out. The study was performed on both the single cylinder and the group of two cylinders, two cylinders were used, one was at the upstream side, and the other was at the downstream side of the flow. They were placed centrally along the flow direction. The inter-spacing space between the two cylinders was varied at 1D, 2D, 3D, 4D, 5D, 6D, 7D and 8D, where D is the width of the cylinder across the flow direction. The pressure coefficients were calculated from the measured values of the surface static pressure distribution on the cylinder. Then the drag and lift coefficients were obtained from the pressure coefficients by the numerical integration method. It was observed that at various angles of attack, the values of the lift coefficients and drag coefficients were insignificant compared to those for a sharp-edged square cylinder. The strength of the vortex shedding was shown to be reduced as the intensity of the incident turbulence was increased. Measurements of drag at various angles of attack (0° to 40°) showed that with increase in turbulence level the minimum drag occurred at smaller values of angle of attack.

A numerical analysis is carried out to demonstrate the variation of two hemodynamic forces: wallshear stress and pressure in the flow field of stenotic artery. The artery has 75% stenosis severity withaxisymmetric cosine shaped stenosis. The wall of the vessel is considered to be rigid. A sinusoidal pulsatile flowis assumed as inlet boundary condition. During the simulation both standard k-? model of low Reynoldscorrection and standard k-? model are used. Some analysis with standard k-? model with low Reynoldscorrection show better agreement with previous experimental results. The peak wall shear stress is found to belocated proximal to the stenosis throat. The results from the standard k-? turbulence model illustratesoscillating wall shear stress downstream the stenosis throat throughout the time period. The pressure gradientat the throat is highest at peak flow condition. These factors contribute to further growth and rupture ofplaques.DOI: http://dx.doi.org/10.3329/jme.v43i1.15780

The static pressure distributions on a single of cylinder with octagonal cross-section having rounded corners are presented. The test was conducted in an open circuit wind tunnel at a Reynolds number of 4.13 x 104 based on the face width of the cylinder across the flow direction in a uniform flow velocity of 13.2 m/s. The experimental test was carried out on a single cylinder at various angles of attack from 0° to 40° at a step of 5°. It was observed that with the rounded corners the drag on the cylinders reduces remarkably in comparison to that on the sharp-edged cylinders. It was also observed that at various angles of attack, the values of the lift coefficients were insignificant compared to those for a sharp-edged square cylinder. The results are applicable to combination of tall buildings one behind the other along the wind velocity direction and each building of square or octagonal cross-section having rounded corners. The wind load on the downstream cylinder decreases remarkably due to the presence of the cylinder in the upstream side.DOI: http://dx.doi.org/10.3329/jme.v43i1.15767

Induced drag is the result of wingtip vortex produced from generating lift by finite wing. It is one of the main drags that an aircraft wing encounters during flight. It hampers aircraft performance by increasing fuel consumption and reducing endurance, range and speed. Winglets are used to reduce the induced drag. They weakens wingtip vortex and thus reduces induced drag. This paper represents the experimental investigation to reduce induced drag using winglet at the wingtip. A model of tapered wing with curved trailing edge (without winglet) as well as two similar wings with blended winglet and double blended winglet are prepared using NACA 4412 aerofoil in equal span and surface area. All the models are tested in a closed circuit subsonic wind tunnel at air speed of 108 km/h (0.09 Mach). Reynolds number of the flow is 2.28 × 105 on the basis of average chord length of the wings. The point surface static pressures at different angles of attack from −4° to 24° are measured for each of the wing and wingle...

This study focuses on the drag reduction by reducing adverse pressure gradient and delaying the flow separation of 2D NACA 0012 airfoil by moving surface through numerical simulation. Two particular cases are considered here. When ‘single moving surface’ is considered, only one moving surface of 10% of the chord length(c) is placed at upper surface of the airfoil starting from 0.05c to 0.15c. When ‘double moving surface’ is considered, one moving surface of 10% of the chord length is placed at upper surface starting from 0.05c to 0.15c and one moving surface of same size is placed at lower surface from 0.05c to 0.15c. Momentum injection into the flow field moves the separation of boundary layer in the vicinity of trailing edge of the airfoil. By momentum injection through single moving surface with the surface velocity twice the free stream velocity and for different angle of attack it is possible to reduce the average drag coefficient by 23.9%. And for same condition with double moving surface it is possible to reduce the average drag coefficient by 25.9%. For moving surface boundary condition, boundary-layer separation is delayed along the chord length on the upper surface of the airfoil.

In this research work an experiment is conducted to observe the effect of wind load around square and hexagonal shaped cylinders in staggered form. The experiment is performed in an open circuit wind tunnel at a Reynolds number of 4.23×104 based on the face width of the cylinder across the flow direction. The flow velocity has been kept uniform at 14.3 m/s throughout the experiment. The test is conducted for single cylinders first and then in staggered form. The cylinders are rotated to create different angles of attack and the angles are chosen at a definite interval. The static pressure readings are taken at different locations of the cylinder by inclined multi-manometers. From the surface static pressure readings pressure coefficients, drag coefficients and lift coefficients are calculated using numerical integration method. These results will surely help engineers to design buildings more stable against wind load. All the results are expressed in non-dimensional form, so that they can be applied for prototype structures.In this research work an experiment is conducted to observe the effect of wind load around square and hexagonal shaped cylinders in staggered form. The experiment is performed in an open circuit wind tunnel at a Reynolds number of 4.23×104 based on the face width of the cylinder across the flow direction. The flow velocity has been kept uniform at 14.3 m/s throughout the experiment. The test is conducted for single cylinders first and then in staggered form. The cylinders are rotated to create different angles of attack and the angles are chosen at a definite interval. The static pressure readings are taken at different locations of the cylinder by inclined multi-manometers. From the surface static pressure readings pressure coefficients, drag coefficients and lift coefficients are calculated using numerical integration method. These results will surely help engineers to design buildings more stable against wind load. All the results are expressed in non-dimensional form, so that they can be applied for p...

A numerical study is carried out to investigate the pure mixed convection in a lid-driven parallelogram cavity filled with water. Both side walls of the cavity are thermally insulated and the top and the bottom walls are kept at low and high temperature respectively. The top wall is moving along the positive x-axis with a constant speed, while the other walls are stationary. The non-dimensional Navier-Stokes and thermal energy equations governing the fluid flow and heat transfer inside the cavity are formulated for the present problem. Numerical simulation using finite element method is carried out to solve these governing equations for the parametric variations of the governing parameters such as Reynolds (Re) and Grashof (Gr) numbers within the range of 0.1 ≤ Re ≤ 800 and 0.01 ≤ Gr ≤ 6.4 × 105 at unity Richardson number (Ri = 1). The interior angle of the parallelogram cavity is also varied from 60° to 120° in order to investigate the transition characteristics from laminar to chaos at pure mixed convec...

In this research, simulation of wind flow over cylinders in a staggered form was carried out. The study was performed using square, pentagonal and hexagonal cylinders having square cylinder in the upstream and another two hexagonal and pentagonal cylinders in the downstream side. A computational fluid dynamics (CFD) program FLUENT has been used to predict the wind effect on the arrangement based on the face width of the cylinder across the flow direction. In the staggered form angles of attack was varied as 0°, 30°, 45°, 60° respectively. It is found that the drag coefficients are remarkably smaller in case of pentagonal and hexagonal shapes compared to those for a sharp-edged square cylinder and the severity of wind loading reduces from that compared to single free-standing structure. The numerical prediction shows a good agreement with previous experimental measurements of similar group of cylinders in same staggered arrangement.

A numerical analysis is carried out to study the performance of steady laminar mixed convection flow inside a square lid-driven cavity filled with water-Al2O3 nanofluid. The top wall of the cavity is moving at a constant velocity and is heated by an isothermal heat source. Two-dimensional Navier-stokes equations along with the energy equations are solved using Galerkin finite element method. Results are obtained for a range of Reynolds and Grashof numbers by considering with and without the presence of nanoparticles. The parametric studies for a wide range of governing parameters in case of pure mixed convective flow show significant features of the present problem in terms of streamline and isotherm contours, average Nusselt number and average temperature profiles. The computational results indicate that the heat transfer coeffcient is strongly influenced by the above governing parameters at the pure mixed convection regime.

In this research work an experiment is conducted to see the effect of wind loading on square, pentagonal and Hexagonal shape cylinders in staggered form. The experiment is done in an open circuit wind tunnel at a Reynolds number of 4.23×104 based on the face width of the cylinder across the flow direction. The flow velocity has been kept uniform throughout the experiment at 14.3 m/s. The test has been conducted for single cylinders first and then in staggered form. Angle of attack is chosen at a definite interval. The static pressure at different locations of the cylinder is measured by inclined multi-manometer. From the surface static pressure readings pressure coefficients are calculated first, then drag and lift coefficients are calculated using numerical Integration Method. These results will surely help engineers to design buildings with such shapes more efficiently. All the results are expressed in non-dimensional form, so they can be applied for prototype buildings and determine the wind loading at...

Utilization of wind energy has been investigated for a long period of time by different researchers in different ways. Out of which, the Horizontal Axis Wind Turbine and the Vertical Axis Wind Turbine have now advanced design, but still there is scope to improve their efficiency. The Vertical Axis Wind Turbine (VAWT) has the advantage over Horizontal Axis Wind Turbine (HAWT) for working on omnidirectional air flow without any extra control system. A modified H-rotor Darrieus type VAWT is analysed in this paper, which is a lift based wind turbine. The effect of solidity (i.e. chord length, no. of blades) on power coefficient (CP) of H-rotor for different tip speed ratios is numerically investigated. The study is conducted using time dependent RANS equations using SST k-ω model. SIMPLE scheme is used as pressure-velocity coupling and in all cases, the second order upwind discretization scheme is chosen for getting more accurate solution. In results, different parameters are compared, which depict the performance of the modified H-rotor Darrieus type VAWT. Double layered H-rotor having inner layer blades with longer chord gives higher power coefficient than those have inner layer blades with smaller chord.

With the rapid growth of population, design and construction of taller buildings are being emphasized now-a-days. Especially the design of the group of tall buildings is economic to take care of the housing problem of the huge population. As buildings become taller, effect of wind on them also increases. In this research work, experiments have been conducted to investigate the wind effect on a combination of pentagonal and hexagonal cylinders. The test was conducted in an open circuit wind tunnel at a Reynolds number of Re = 4.22 × 104 based on the face width of the cylinder across the flow direction in a uniform flow velocity of 13.5 m/s. A pentagonal cylinder was placed in the upstream and another two hexagonal cylinders were in the downstream. The transverse and longitudinal spacing between the cylinders were varied and the surface static pressures at the different locations of the cylinders were measured with the help of inclined multi-manometers. From the measured values of surface static pressures, ...

Numerical solution based on the control volume method is presented for the study of heat transfer for forced convective flow in a channel filled with a fluid saturated porous media. The solution of the conservative differential equations governing the flow is performed using the SZMPLE algorithm. The wall effects on the variation of porosity and thermal dispersion have been considered. In calculating the thermal dispersive conductivity, a general expression has been obtained taking into account the flow geometry and flow Reynolds number. The expression appears to serve well in the present investigation and also in reproducing the results of previous studies. The analysis includes predictions of temperature profiles and heat flux for the constant wall temperature condition at the wall and have been compared with available experimental data.

This paper reports the performance of an equally spaced vertical axis vane type rotor tested in a wind tunnel. The aerodynamic characteristics i.e. torque coefficient, drag coefficient etc. of a stationary vane type rotor have been studied in this research work by measuring the pressure distribution on the blade surfaces at various rotor angles. The experimental investigation was performed on four bladed vertical axis vane type rotor in a uniform flow jet produced by an open circuit wind tunnel. It has been observed that the static torque varies at different rotor angles. Total static torque coefficient at different rotor angles curve repeats from 0° to 80°, 90° to 170°, 180° to 260° and 270° to 350° angle of rotation. A quasi-steady approach was applied for the prediction of dynamic performance of the rotor using the static drag and torque coefficients. This method results in a fair agreement with the measured power coefficient.

Publisher Summary This chapter throws the attention on wind power utilization for water pumping in Bangladesh. The possibilities of introducing small scale wind power pumping in Bangladesh have been assessed with regard to wind data supplied by the Bangladesh Meteorological Department. The large-scale wind energy extraction is not feasible in Bangladesh due to low wind speed available. However, there is a potential of small scale wind power pumping in some regions in the country if a proper choice of wind turbine is made. The wind turbine may be useful to drive hand pumps used for irrigating agricultural land. The performance of horizontal axis sailwing rotor coupled to a No. 6 hand tubewell is found to be satisfactory. The combined efficiency of the windmill pump set is found to be about 20% at a wind speed of 2.45 m/s. The Reynolds number based on wind speed and rotor swept diameter is in the range of 4.67e5 to 1.87e6.

The details on breakup processes of liquid column and sheet are numerically investigated to provide the physics of the capillary instabilities and formation of liquid drops. Two cases are used: A numerical analysis on the capillary instabilities and breakup processes of a cylindrical liquid column and a moving liquid sheet in a moving gaseous medium to analyze the dynamics and breakup of the liquid sheet. The problem, composed of the Navier-Stokes systems associated with surface tension forces, is solved by the Volume of Fluid (VOF) technique with a Continuum Surface Force (CSF) to artificially smooth the discontinuity present at the interface. The results show that before disintegration of the liquid the capillary waves become unstable and the source of making the wave unstable is inherently developed by the system. The investigation of moving liquid sheet showed that the two modes of forces for liquid stretching exists: shear force causing the stretching of liquid by shear velocity and drag force causing the stretching of liquid by gas velocity ahead of the tip of the liquid sheets. Stretching of liquid by shear force causes the protrusion of liquid from the tip of liquid sheet and the surface tension force causes the tip of the sheet to make it round. It can also be revealed that the aerodynamic force at the tip of the sheet plays an important role to continue the stretching of sheet and controls the formation of droplet with the occurrence of sheet breakup.

An experimental investigation of mean pressure distributions on a group of cylinders with square and rectangular cross-sections in a uniform cross flow is presented here. The group consists of one rectangular and two square cylinders of identical dimension. The rectangular cylinder is placed centrally in the upstream side and the other two square cylinders are placed symmetrically in the downstream side with respect to tunnel axis. Surface pressure distributions on the cylinders are measured for various longitudinal spacings of the cylinders. Wind loads are obtained in terms of drag coefficients, lift coefficients and total force coefficients. The drag on an isolated cylinder is higher in general than that on the same cylinder while it becomes part of a group. Keywords: Wind load, staggered cylinders. DOI: 10.3329/jme.v38i0.901 Journal of Mechanical Engineering Vol.38 Dec. 2007 pp.52-57

This paper explains the fabrication of an UAV having aerofoil shaped fuselage using NACA 4416 profile and compare the result between the aerodynamic characteristics with that of the same model obtained from CFD investigation. Open circuit subsonic wind tunnel has been used to test the fabricated UAV model and collection of data. The wind tunnel is associated with Versatile Data Acquisition System (VDAS) to measure the lift & drag force coefficients and point surface pressures. This paper explains the design parameters and investigation of the aerodynamic characteristics of the fabricated ‘Aerofoil Shaped Fuselage’ UAV model. This type of model might be used for many military and civil applications like scientific data gathering, surveillance for law enforcement & homeland security, precision agriculture, forest fire monitoring, geological survey etc. The aerodynamic characteristics of Aerofoil Shaped Fuselage UAV model have been carried out at two different Reynolds Number (1.37 x 10 5 and 2.74 x 10 5 respectively) with different angles of attack from -3 o to 18 o . The stalling angle of this design is found at about 14 o during experimental investigation. The aerofoil shaped fuselage UAV model might be used for designing the future UAV.

In this research work, an experimental investigation of wind effect on pentagonal and hexagonal staggered cylinders was carried out. The study was performed on the group consisting of three cylinders, arranged in staggered form, one pentagonal cylinder in the upstream and another two hexagonal cylinder in the downstream side. The test was conducted in an open circuit wind tunnel at a Reynolds number of 4.22 x 10 4 based on the face width of the cylinder across the flow direction in a uniform flow velocity of 13.5 m/s. The group of three cylinders was taken into consideration for the study and the surface static pressures were measured for various transverse spacing of 2D, 3D, 5D and longitudinal spacing of 1D, 2D, 4D, 6D, 8D, where D is the width of the cylinder across the flow direction. The surface static pressures at the different locations of the cylinder were measured with the help of inclined multi-manometers. The pressure coefficients were calculated from the measured values of the surface static pressure distribution on the cylinder. Later the drag and lift coefficients were obtained from the pressure coefficients by the numerical integration method. The results will enable the engineers and architects to design buildings more efficiently. Since the results will be expressed in the non-dimensional form they may be applied for the prototype building.

At present Closed Loop Pulsating Heat Pipe (CLPHP) is a novel cooling strategy for successful thermal management though it is a complex heat transfer device having a strong thermo-hydrodynamic coupling to govern the thermal performance. This research is to study the effect of inclination angle and working fluid on the heat transfer characteristics and performance of CLPHP. The performance characterization has been done using two different working fluids of water and ethanol with inclination angle of 0˚ (vertical), 30˚, 45˚, 60˚, 75˚ and 90˚ (horizontal). The experiment is conducted on a CLPHP made of 148 cm long copper capillary tube of 3.0 mm outer diameter and 2.0 mm inner diameter creating a total of 13 turns. The total length of evaporator section is 39.5 cm and condenser section is 31.5 cm; while the rest is assumed to be adiabatic. The evaporator section is heated by electrical heat input, while the condenser section is cooled by atmospheric air flow. Since a PHP is recognized as a two phase heat transfer device, for comparative studies it is operated as a double-phase system by filling it 70% with the working fluid. The comparative study results in a better understanding of the underlying physics of the PHP operation. The experimental results indicate a strong influence of gravity and thermo physical properties of the working fluid on the performance of the CLPHP. The results demonstrate the effect of the input heat flux, inclination angle and physiochemical properties of the working fluid on the thermal performance of the device.