Aerodynamics of plunging airfoil in wind gust

2018 ◽  
Vol 90 (7) ◽  
pp. 1050-1064 ◽  
Author(s):  
Arpan Das ◽  
Shaligram Tiwari
Keyword(s):  
Navier Stokes ◽  
Wind Gust ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Freestream Velocity ◽  
Content Type ◽  
Naca0012 Airfoil ◽  
Reduced Frequency ◽  
Aerial Vehicle ◽  
Lift And Drag

Purpose Growing application of micro aerial vehicle (MAV) sets in demand for accurate computations of low Reynolds number flows past their wings. The purpose of this study is to investigate the effect of unsteady freestream velocity or wind gust on a harmonically plunging symmetric NACA0012 airfoil at Re = 1,000. The influence of unsteady parameters, such as reduced frequency of plunging motion (0.25 < k < 1.5), non-dimensional plunging amplitude (ho = 0.2) and non-dimensional amplitude of wind gust (0.1 = λ = 0.4) has been studied. Design/methodology/approach Computations have been carried out using commercial software ANSYS Fluent 16.0. To incorporate the plunging motion, the entire reference frame is oscillating, and thereby, a source term is added in the Navier–Stokes equation. Findings The results have been presented in the form of streamlines, vorticity contours, lift and drag signals and their spectra. It is observed that the ratio of plunging frequency to gust frequency (f/fg) has strong influence on periodic characteristics of unsteady wake. It has also been observed that for a fixed plunging amplitude, an increase in value of k results into a change from positive drag to thrust. Practical implications The research has implications in the development of MAV. Originality/value This study is intended to get a better understanding of unsteady parameters associated with gusty flow in flapping wing applications and possible ways to alleviate its adverse effect on it.

Numerical Study on Control of Sunroof Buffeting

2021 ◽  
Vol 13 (2) ◽  
Author(s):  
K. Vijaykumar ◽  
S. Poonkodi ◽  
A.T. Sriram
Keyword(s):  
Numerical Study ◽  
Leading Edge ◽  
Dominant Frequency ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Flow Modification ◽  
Numerical Result ◽  
Modification Technique ◽  
Commercial Solver

Sunroof has become one of the essential features of a luxury car, and it provides natural air circulation and good illumination into the car. But the primary problem associated with it is the buffeting noise which causes discomfort to the passengers. Though adequate studies were carried out on sunroof buffeting, efficient control techniques are needed to be developed from fundamental mechanism. To reduce the buffeting noise, flow modifications at the entrance of the sunroof is considered in this study. The internal portion of the car with sunroof is simplified into a shear driven open cavity, and two-dimensional numerical simulations are carried out using commercial solver, ANSYS Fluent. Reynolds averaged Navier-Stokes equation is used with the realizable k-? turbulence model. The unsteady numerical result obtained in this study is validated with the available experimental results for the dominant frequency. The prediction is good agreement with experiment. Flow modification technique is proposed to control the sunroof buffeting by implementing geometric modifications. A hump has been placed near the leading edge of the cavity which resulted in significant reduction of pressure oscillations. Parametric studies have been performed by varying the height of hump and the distance of hump from the leading edge. There is no prominent difference when the height of the hump is varied. As the distance of the hump from the leading edge is reduced, the sound pressure level decreases.

Conjugate Free Convection Heat Transfer and Thermodynamic Analysis of Infrared Suppression Device with Cylindrical Funnels

2022 ◽  
Author(s):  
Vikrant Chandrakar ◽  
Arnab Mukherjee ◽  
Jnana Ranjan Senapati ◽  
Ashok Kumar Barik
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Convection Heat Transfer ◽  
Navier Stokes ◽  
Bejan Number ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Geometric Ratio ◽  
Flow Rate Increase ◽  
Free Convection Heat

Abstract A convection system can be designed as an energy-efficient one by making a considerable reduction in exergy losses. In this context, entropy generation analysis is performed on the infrared suppression system numerically. In addition, results due to heat transfer are also shown. The numerical solution of the Navier-stokes equation, energy equation, and turbulence equation is executed using ANSYS Fluent 15.0. To perform the numerical analysis, different parameters such as the number of funnels, Rayleigh number (Ra), inner surface temperature, and geometric ratio are varied in the practical range. Results are shown in terms of heat transfer, entropy generation, irreversibility (due to heat transfer and fluid friction), and Bejan number with some relevant parameters. Streamlines and temperature contours are also provided for better visualization of temperature and flow field around the device. Results show that heat transfer and mass flow rate increase with the increase in Ra. Entropy generation and the irreversibility rise with an increase in the number of funnels and geometric ratio. Also, the Bejan number decreases with an increase in Ra and the number of funnels. A cooling time is also obtained using the lumped capacitance method.

Numerical investigation of an anti-icing method on airfoil based on the NSDBD plasma actuator

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Junjie Niu ◽  
Weimin Sang ◽  
Feng Zhou ◽  
Dong Li
Keyword(s):  
Phenomenological Model ◽  
Stokes Equations ◽  
Pulse Repetition Frequency ◽  
Leading Edge ◽  
Pulse Frequency ◽  
Plasma Actuator ◽  
Navier Stokes ◽  
Peak Voltage ◽  
Content Type ◽  
Naca0012 Airfoil

Purpose This paper aims to investigate the anti-icing performance of the nanosecond dielectric barrier discharge (NSDBD) plasma actuator. Design/methodology/approach With the Lagrangian approach and the Messinger model, two different ice shapes known as rime and glaze icing are predicted. The air heating in the boundary layer over a flat plate has been simulated using a phenomenological model of the NSDBD plasma. The NSDBD plasma actuators are planted in the leading edge anti-icing area of NACA0012 airfoil. Combining the unsteady Reynolds-averaged Navier–Stokes equations and the phenomenological model, the flow field around the airfoil is simulated and the effects of the peak voltage, the pulse repetition frequency and the direction arrangement of the NSDBD on anti-icing performance are numerically investigated, respectively. Findings The agreement between the numerical results and the experimental data indicates that the present method is accurate. The results show that there is hot air covering the anti-icing area. The increase of the peak voltage and pulse frequency improves the anti-icing performance, and the direction arrangement of NSDBD also influences the anti-icing performance. Originality/value A numerical strategy is developed combining the icing algorithm with the phenomenological model. The effects of three parameters of NSDBD on anti-icing performance are discussed. The predicted results show that the anti-icing method is effective and may be helpful for the design of the anti-icing system of the unmanned aerial vehicle.

scholarly journals Choke flutter instability sources tracking with linearized calculations

2019 ◽  
Vol 30 (9) ◽  
pp. 4155-4166
Author(s):  
Pierre Duquesne ◽  
Quentin Rendu ◽  
Stephane Aubert ◽  
Pascal Ferrand
Keyword(s):  
Shock Wave ◽  
Superposition Principle ◽  
Strong Shock ◽  
Source Tracking ◽  
Navier Stokes ◽  
Test Case ◽  
Navier Stokes Equation ◽  
Local Vibration ◽  
Limited Region ◽  
Content Type

Purpose The choke flutter is a fluid-structure interaction that can lead to the failure of fan or compressor blade in turbojet engines. In ultra high bypass ratio (UHBR) fans, the choke flutter appears at part-speed regimes and at low or negative incidence when a strong shock-wave chokes the blade to blade channel. The purpose of this study is to locate the main excitation sources and improving the understanding of the different work exchange mechanisms. This work contributes to avoiding deficient and dangerous fan design. Design/methodology/approach In this paper, an UHBR fan is analyzed using a time-linearized Reynolds-averaged Navier–Stokes equation solver to investigate the choke flutter. The steady-state and the imposed vibration (inter blade phase angle, reduced frequency and mode shape) are selected to be in choke flutter situation. Superposition principle induced by the linearization allow to decompose the blade in numerous small subsections to track the contribution of each local vibration to the global damping. All simulations have been performed on a two-dimensional blade to blade extraction. Findings Result analysis points to a restricted number of excitation sources at the trailing edge which induce a large part of the work exchange in a limited region of the airfoil. Main phenomena suspected are the shock-wave motion and the shock-wave/boundary layer interaction. Originality/value An original excitation source tracking methodology allowed by the linearized calculation is addressed and applied to a UHBR fan test case.

scholarly journals Effect of Leading-Edge Bulges on Aerodynamic Characteristics of Bionic Wingsail

2021 ◽  
Author(s):  
Chen Li ◽  
Peiting Sun ◽  
Hongming Wang
Keyword(s):  
Stokes Equations ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Suction Surface ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Extension Direction ◽  
Lift And Drag

The leading-edge bulges along the extension direction are designed on the marine wingsail. The height and the spanwise wavelength of the protuberances are 0.1c and 0.25c, respectively. At Reynolds number Re=5×105, the Reynolds Averaged Navier-Stokes equations are applied to the simulation of the wingsail with the bulges thanks to ANSYS Fluent finite-volume solver based on the SST K-ω models. The grid independence analysis is carried out with the lift and drag coefficients of the wingsail at AOA = 8° and AOA=20°. The results show that while the efficiency of the wingsail is reduced by devising the leading-edge bulges before stall, the bulges help to improve the lift coefficient of the wingsail when stalling. At AOA=22° under the action of the leading-edge tubercles, a convective vortex is formed on the suction surface of the modified wingsail, which reduces the flow loss. So the bulges of the wingsail can delay the stall.

scholarly journals Numerical modelling of non-premixed biogas and LPG combustion to study carbon nanostructures formation in flame

2021 ◽  
Author(s):  
Manpreet Kaur ◽  
◽  
Jyoti Bharj ◽  
Rabinder S. Bharj ◽  
Rajan Kumar ◽  
...  
Keyword(s):  
Carbon Nanostructures ◽  
Diffusion Flames ◽  
Soot Formation ◽  
Flame Temperature ◽  
Chemical Species ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Burner Exit ◽  
Fuel Flow

This work presents the numerical simulation of biogas and LPG fuelled diffusion flames in an axisymmetric chamber to study in-depth, the formation mechanism of soot and carbon nanostructures in these flames. The simulation is formulated on the set of transport equations that involve the equations for conservation of mass (the continuity equation), momentum (Navier-Stokes equation), energy, and chemical species. The governing equations are solved using ANSYS FLUENT, which is centered on the finite volume method. To predict the soot formation, one step soot model has been incorporated. The solution of these equations permits the estimation of temperature field and species concentrations inside the flame. Simulation is conducted at fixed fuel flow rate and varied oxygen flow rates. The results reveal that the formation of soot and carbon nanostructures is strongly dependent on peak flame temperature and concentration of precursor species formed in the flame. Since two fuels produce an exclusive chemical environment in the flame, the flame temperature and CO concentration that is conducive to the growth of carbon nanostructures is higher for LPG fuel as compared to that for biogas. Hence, the nucleation process of carbon nanostructures is faster for LPG than biogas. Moreover, the reactions taking place inside the flame at different locations can also be predicted from flame temperature and species concentration at that location. Pyrolysis of fuel occur near the burner exit, followed by the nucleation and surface growth of carbon nanostructures in the nearby region and oxidation of formed carbon nanostructures near the flame tip.

Numerical investigation on implication of innovative hydrogen strut injector on performance and combustion characteristics in a scramjet combustor

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sribhashyam Krishna Kireeti ◽  
Gadepalli Ravikiran Sastry ◽  
Santosh Kumar Gugulothu
Keyword(s):  
Transport Model ◽  
Weight Ratio ◽  
Combustion Efficiency ◽  
Navier Stokes ◽  
Mixing Efficiency ◽  
Injection Technique ◽  
Mixing Rate ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Scramjet Combustor

Abstract A detailed numerical analysis on a scramjet combustor is carried out by introducing an innovative shaped strut in place of the conventional strut. The design of newly added strut aids in generating intense vorticity which helps in efficient mixing of fuel and oxidizer. The air from the isolator enters the combustor at Mach 2.0, whereas fuel enters from the trailing edge of the strut sonically. In this study the flow dynamics with finite volume approach on commercial software Ansys-Fluent 20.0 to solve the two-dimensional Reynolds average Navier Stokes equation (RANS) with compressible fluid flow by considering the density-based solver with SST k-ε turbulent model. The species transport model with volumetric reaction and finite rate/eddy dissipation turbulence chemistry interaction is adopted to study the combustion phenomena and validated with the experimental results, and it is found that the interaction of the shear shock layer enhances the mixing rate by intensifying turbulence. The modified strut injector’s mixing efficiency is compared to the base strut and observed that with a 40% reduction in length, the modified strut injection technique exhibited a mixing efficiency of >95%. The combustion efficiency is then estimated streamwise, and the plot follows the same pattern as the mixing efficiency with fuel burns down completely when x = 150 mm for the modified strut whereas x = 200 mm for the base strut. This can compact the combustion chamber and increases the thrust-to-weight ratio. So, the innovative strut adopted can improvise the combustion efficiency.

Flow control method by applying flexible shells procedure in transonic flow

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
M.R. Saber ◽  
M.H. Djavareshkian
Keyword(s):  
Drag Force ◽  
Smart Materials ◽  
Transonic Flow ◽  
Stokes Equations ◽  
Control Method ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Content Type ◽  
Flexible Shells

Purpose In the present research, the effect of the flexible shells method in unsteady viscous flow around airfoil has been studied. In the presented algorithm, due to the interaction of the aerodynamic forces and the structural stiffness (fluid-structural interaction), a geometrical deformation as the bump is created in the area where the shock occurs. This bump causes instead of compressive waves, a series of expansion waves that produce less drag and also improve the aerodynamic performance to be formed. The purpose of this paper is to reduce wave drag throughout the flight range. By using this method, we can be more effective than recent methods throughout the flight because if there is a shock, a bump will form in that area, and if the shock does not occur, the shape of the airfoil will not change. Design/methodology/approach In this simulation pressure-based procedure to solve the Navier-Stokes equation with collocated finite volume formulation has been developed. For this purpose, a high-resolution scheme for fluid and structure simulation in transonic flows with an arbitrary Lagrangian-Eulerian method is considered. To simulate Navier-Stokes equations large eddy simulation model for compressible flow is used. Findings A new concept has been defined to reduce the transonic flow drag. To reduce drag force and increase the performance of airfoil in transonic flow, the shell can be considered flexible in the area of shock on the airfoil surface. This method refers to the use of smart materials in the aircraft wing shell. Originality/value The value of the paper is to develop a new approach to improve the aerodynamic performance and reduce drag force and the efficiency of the method throughout the flight. It is noticeable that the new algorithm can detect the shock region automatically; this point was disregarded in the previous studies. It is hoped that this research will open a door to significantly enhance transonic airfoil performance.

Influence of innovative hydrogen multi strut injector with different spacing on cavity-based scramjet combustor

2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Sribhashyam K. Kireeti ◽  
Ravikiran Sastry Gadepalli ◽  
Santhosh K. Gugulothu
Keyword(s):  
Recirculation Zone ◽  
Transport Model ◽  
Combustion Efficiency ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Scramjet Combustor ◽  
Separation Layers ◽  
Finite Volume Approach ◽  
And Performance

Abstract In this study, the flow dynamics with finite volume approach on commercial software Ansys-Fluent 20.0 to solve the compressible two-dimensional fluid flow with Reynolds Average Navier Stokes equation (RANS) equation by considering the density-based solver with Shaer stress transport model (SST) k- ω turbulent model. The species transport model with volumetric reaction and finite rate/eddy dissipation turbulence chemistry interaction is adopted to study the combustion phenomena. Additionally, the effect of spacing between the struts on the flow characters and performance of the combustor is studied by increasing the spacing of struts from 1 mm to 4 mm for each increment of 1 mm. It is found that the multi strut improves the mixing and combustion efficiency compared with that of the single strut owing to the formation of a significant separation layer, resulting in multiple shocks, vortices, and a larger recirculation zone. However, when the spacing of struts is increased further, the performance of the combustor is found to be deteriorating owing to the formation of larger separation layers. The recirculation zone is significant when the strut spacing is minimal and shrinks and restricts itself within the cavity when spacing is increased. So, for better performance of combustor, multi strut with minimum spacing is preferable.

scholarly journals Hydrodynamic Performance of Rectangular Heaving Buoys for an Integrated Floating Breakwater

2019 ◽  
Vol 7 (8) ◽  
pp. 239 ◽  
Author(s):  
Xiaoxia Zhang ◽  
Qiang Zeng ◽  
Zhen Liu
Keyword(s):  
Wave Energy ◽  
Numerical Results ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Wave Energy Converters ◽  
Floating Breakwater ◽  
Reaction Forces ◽  
Wave Conditions

Recently, the integrated development of wave energy converters and breakwaters has become popular, moving from traditional passive wave absorption to active energy capture. In this study, rectangular heaving buoys are considered as floating breakwater modules to absorb wave energy. A numerical wave tank is established based on Reynolds Averaged Navier-Stokes equation and User-Define-Function in ANSYS-Fluent commercial software. The numerical results show that incident wave conditions and submerged depth have significant effects on the heaving performance and wave energy absorption of a rectangular buoy. Flow structures around the buoy are shown to exhibit flow separations and vortex shedding, which can provide more information on buoy optimization. Power take-off (PTO) reaction forces are assumed to be a linear function of the translation velocities of the buoy. Numerical results demonstrate that a suitable PTO module can improve the wave power absorption by up to 34.2% for certain buoy and wave conditions, which is valuable for further investigations.

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