Pressure Plots Research Articles

Gas hydrate inhibition: performance of an agro-waste based locally formulated inhibitor

This paper compares the inhibitory capacity of two conventional kinetic hydrate inhibitors (KHIs), N-Vinylcaprolactam (N-VCap) and 2-Di(methylamino)ethyl Methacrylate (2-DMEM) with a Kinetic Hydrate Inhibitor developed locally from agro waste-based material. The Experiments were carried out using a 316 stainless steel laboratory mini flow loop, skid mounted on an external metal framework using 0.01-0.03 weight percentages of the various inhibitors. Plots of pressure versus time, temperature versus time and initial and final pressures showed the locally developed kinetic hydrate inhibitor (LDKHI) to be a better inhibitor with pressure decreasing from 150 psi to 122, 127 and 120 psi for 0.01 - 0.03 wt% respectively. Forthe same range of concentrations, N-VCap had pressure values of 114, 124 and 117 psi while that of 2-DMEM were 95, 120 and 116 psi, respectively. Optimum dosage of LDKHI was 127 psi at 0.02 wt%. For 0.01 to 0.03 wt% concentrations of all the inhibitors, LDKHI remained the best in minimizing the loop pressure drop as indicated by high volume of gas present in the loop at the end of 120 minutes. Inhibition efficiency versus weight percentages plot clearly showed that LDKHI performed better than the conventional kinetic inhibitors having inhibition efficiencies of 75.44, 79.82 and 73.68%. NV-Cap had values of 68.42, 77.19 and 71.05% and 2-DMEM inhibited system had values of 51.75, 73.68 and 70.18% for 0.01, 0.02 and 0.03 wt% respectively. These values for LDKHI are the highest compared to those of N-VCap and 2-DMEM respectively. The LDKHI is eco-friendly, biodegradable, readily available and water-soluble so it should be harnessed and considered for field trial.

Early detection of the combustion instabilities by quantifying diagonal-wise measurements of joint recurrence plots of pressure and radiant energy fluctuations

This article presents a study of the early detection of combustion instabilities of a 250 kW liquid rapid premixed oil swirled burner. The main objective was the calculation of indexes, based on a chaotic analysis, able to detect in advance the combustion instabilities. In the combustor, the air mass flow rate was kept constant, and in order to induce the combustion instabilities, the fuel mass flow rate was adjusted during the experiments in which pressure and radiant energy fluctuations were simultaneously measured from the combustion chamber. In this chaotic analysis, joint recurrence plots were calculated in order to analyze the dependence between the pressure and radiant energy fluctuations. Hence, a diagonal-wise quantification was applied to the joint recurrence plots to calculate four indexes: the τ-recurrence rate index RRτ, the τ-determinism index DETτ, the τ-average diagonal line length index Lτ, and the τ-entropy index sτ. The results show that all four indexes were capable of sorting all cases under analysis into two groups: the “combustion noise regime” due to the low-amplitude aperiodic oscillations and the “combustion instability regime” due to the high-amplitude periodic oscillations. In addition, early detection of the transitions were also detected. Therefore, the results presented in this research showed that the four indexes were effective precursors in order to detect in advance the combustion instabilities.

Effect of Thiouronium-Based Ionic Liquids on the Formation and Growth of CO2 (sI) and THF (sII) Hydrates.

In this manuscript, two thiouronium-based ionic liquids (ILs), namely 2-ethylthiouronium bromide [C2th][Br] and 2-(hydroxyethyl)thiouronium bromide [C2OHth][Br], were tested at different concentrations (1 and 10 wt%) for their ability to affect CO2 (sI) and tetrahydrofuran (THF) (sII) hydrate formation and growth. Two different methods were selected to perform a thermodynamic and kinetic screening of the CO2 hydrates using a rocking cell apparatus: (i) an isochoric pressure search method to map the hydrate phase behavior and (ii) a constant ramping method to obtain the hydrate formation and dissociation onset temperatures. A THF hydrate crystal growth method was also used to determine the effectiveness of the ILs in altering the growth of type sII hydrates at atmospheric pressure. Hydrate–liquid–vapor equilibrium measurements revealed that both ILs act as thermodynamic inhibitors at 10 wt% and suppress the CO2 hydrate equilibria ~1.2 °C. The constant ramping methodology provides interesting results and reveals that [C2OHth][Br] suppresses the nucleation onset temperature and delays the decomposition onset temperatures of CO2 hydrates at 1 wt%, whereas suppression by [C2th][Br] was not statistically significant. Normalized pressure plots indicate that the presence of the ILs slowed down the growth as well as the decomposition rates of CO2 hydrates due to the lower quantity of hydrate formed in the presence of 1 wt% ILs. The ILs were also found to be effective in inhibiting the growth of type sII THF hydrates without affecting their morphology. Therefore, the studied thiouronium ILs can be used as potential dual-function hydrate inhibitors. This work also emphasizes the importance of the methods and conditions used to screen an additive for altering hydrate formation and growth.

Mitigation of long-term station blackout accident of advanced boiling water reactors

Taiwan Power Company proposed ultimate response guidelines (URGs) to mitigate the so-called ‘Fukushima type accident’ of nuclear power plants. As stipulated in URGs, operators will depressurize the reactor coolant system if necessary to bring in low-pressure water. Containment venting is then used to dissipate the heat generated from the decay. These collective actions are called DIVing (depressurizing, injecting and venting) in URGs. The actions are designed to avoid large-scale evacuation of the public around the damaged plant during an accident. In this study, the effectiveness of DIVing in preventing radioactive emission to the environment is evaluated using RELAP5 codes. The plant analyzed is Lungmen Nuclear Power Station, which has two 1350-MWe advanced boiling water reactors (ABWR) designed by General Electric. In the Standard Operating Procedure of DIVing in URGs, controlled depressurization is executed to bring the pressure to the lowest operating pressure of Reactor Core Isolation Cooling (RCIC) system. The core water level is kept high while RCIC is in operation.. Emergency depressurization is carried out when RCIC fails. The executing time of DIVing as specified in URGs is too conservative. The study identifies the acceptable initial states for operators to carry out DIVing actions. The success criterion is to keep the peak cladding temperature below 1088 K (1500°F) during the transient, which is the temperature of cladding breach and the initiation of gap release of radionuclide from fuel rod.In this study, depressurization transients in the station blackout accident of ABWR are simulated using RELAP5/3D. The results show that the peak cladding temperature obtained during a depressurization transient depends on the time of depressurization, initial pressure, initial water level and injection rate of low-pressure water. When the water level and injection rate are fixed, a region of successful depressurization on the depressurization time vs pressure plot is delineated based on the results of RELAP5 simulations. Regions of successfully depressurization for typical combinations of injection rate and water level are identified, and acceptable region’s boundary is linear.A computation aid, Guidance for Emergency Depressurization (GfED), was developed based on the simulation results of the RELAP5/3D code to assist operators in determining whether the emergency depressurization under given conditions can be performed successfully. GfED uses low-pressure injection flow rate, water level and initial pressure upon emergency depressurization as input parameters to calculate the latest time that is acceptable for emergency depressurization. The technique of linear interpolation is adopted. By comparing the result and value input by the operators, GfED can predict whether it is safe to depressurize.GfED also guides operators to determine the initial condition of a successful depressurization. Three of the four input parameters are fixed in the guidance, and the limiting value of the fourth parameter of a successful depressurization is calculated. These values are informative for operators to manoeuvre the system while the reactor core isolation cooling system is still running.

Analysis of a Hypothetical Complete Loss-of-Coolant Accident in a Typical Research Reactor

In the present study, an analysis of a hypothetical complete loss-of-coolant accident in a typical open-pool research reactor is conducted. The reactor core is assumed to be completely uncovered and exposed to the ambient air. The possibility of passively cooling the decay heat of the exposed reactor core by natural convection to air and thermal radiation until core reflooding is investigated. A three-dimensional computational fluid dynamics analysis is conducted for the uncovered core while cooled by air natural convection and thermal radiation. The reactor core is simulated as a porous zone with decay heat generation specified as a cosine-shape distribution. The reactor core decay heat acts as a driving force for the coolant flow from the cold leg to the hot leg. The thermal equilibrium porous media model is used to represent the energy equation inside the core region. This study is conducted for core uncover time (the time interval between reactor shutdown and the moment when the reactor core is drained of water) of 10E3, 10E4, 10E5, 10E6, 10E7, and 10E8 s. Contour plots of temperature, velocity, density, and pressure at different values of core uncover time are illustrated. It’s found that for core uncover times of 10E3, and 10E4 s, the maximum core temperature exceeds the cladding melting point. The core maximum temperature is well below the melting point for uncover times of 10E5, 10E6, 10E7, and 10E8 s.

Tuning of the microstructural and electrical properties of undoped BaTiO3 by spark plasma sintering

The distribution of oxygen vacancies in BaTiO3 specimens can greatly affect material electrical properties. Spark plasma sintering followed by annealing in controlled pO2 atmospheres offers the potential to control the oxygen vacancy distribution. Impedance spectroscopy has been used to study the electrical characteristics of undoped BaTiO3 specimens prepared at 1200 °C under a pressing pressure of 5 MPa and 50 MPa using spark plasma sintering (SPS). For both samples, at temperatures greater than 750 °C, the total conductivity is determined by the bulk conductivity (σb), while at temperatures between 550 °C–750 °C the total conductivity is determined by the grain boundary conductivity (σgb). Below 550 °C, the total conductivity is determined by the BaTiO3–Pt interface conductivity (σel). The bulk, grain boundary and electrode interface resistances and activation energies are lower for samples sintered and pressed at 50 MPa, compared to specimens sintered and pressed at 5 MPa. Plots of grain boundary conductivity (σgb) vs. oxygen partial pressure (pO2) (log(σgb) vs. log(pO2)), over the temperature range 517 °C–683 °C, have slopes of approximately 4.0 indicating that doubly charged oxygen vacancies (VO••) are located at the grain boundaries. The grain boundary region and BaTiO3–Pt interface conductivities are highly sensitive to the oxygen partial pressure. Therefore, SPS sintered BaTiO3 specimens that have been subjected to controlled annealing could be used to tailor BaTiO3 dielectric properties, as well as have potential applications in high temperature O2 sensing. Furthermore, analysis of a.c. conductivity using the Jonscher model reveals that the governing charge transport mechanism is via quantum mechanical tunneling (QMT), which operates at temperatures when grain boundaries control the total conductivity. The mechanism switches to the correlated barrier hopping (CBH) model at temperatures when the bulk controls the total conductivity.

Dry wear response of a Zn-based alloy containing 37.5% Al as affected by sliding conditions

Abstract This paper discusses the observations made pertaining to dry sliding wear characteristics of a Zn-based alloy at different sliding speeds and pressures. The wear rate increased with speed and pressure. The wear rate versus pressure plots attained two slopes wherein the slope was low up to a specific pressure followed by an increased slope at still higher pressures. This trend was observed at all the sliding speeds except the maximum; in the latter case one slope (identical to that of the higher slope at the lower speeds) only was noted. The seizure pressure was noted to decrease with speed. The temperature near the specimen surface increased with test duration, pressure and sliding speed. The rate of temperature increase was significantly high initially. This was followed by a lower rate of increase in temperature at longer test durations. In some cases, the rate of temperature increase became high once again towards the end of the tests. The influence of applied pressure and sliding speed on the temperature increase was practically identical to that on wear rate. Lower wear rate of the alloy agreed with less surface/subsurface damage and finer debris formation and vice versa.

Pressure-induced phase transitions in MBANP crystal: A study by synchrotron radiation X-ray diffraction and Raman spectroscopy

Raman spectroscopy and synchrotron radiation X-ray diffraction have been used to study the effect of pressure on 2-(-α-methylbenzylamino)-5-dinitropyridine (MBANP). Several changes are observed with increasing pressure in the Raman spectra of this system, such as splitting of various bands and disappearance of bands. Discontinuous shifts in wavenumber vs pressure plot indicate that a conformational phase transition takes place around 0.5 GPa. The behavior of the Raman spectra indicates that MBANP molecules present conformational phase transition at high-pressure. X-ray diffraction, performed with synchrotron radiation, confirms the conformational changes observed by Raman experiments around 0.5 GPa. The pressure provokes a rotational movement of the benzene ring which can be associated with the conformational phase transition.

Analysis of shock wave-boundary layer interaction in a shock tube using higher order scheme

Over the last couple of decades, the shock-wave boundary-layer interaction has gained a lot of attention due to its practical importance in many engineering applications. It is a complex problem involving shock-wave bifurcation, boundary-layer separation, the interaction of contact discontinuity with the shock wave, the formation of shocklets, and the evolution of vortical structures having different length scales. It is difficult to capture experimentally the detailed flow field having the shocklets and vortices. Numerical solvers having negligible numerical dissipation are highly essential to predict these structures accurately. Over the years, many researchers have obtained a grid-converged solution for shock-wave boundary-layer interaction at Reynolds numbers of 200 and 1000. The shock-wave boundary-layer interaction at higher Reynolds numbers is not attempted due to the requirement of huge computational resources and challenges associated with convergence. In the investigation, the grid-converged solution is obtained for a Reynolds number of 2500 with a 13th order high-resolution hybrid scheme using 100 cores of a computational cluster equipped with 3.0 GHz Intel Xeon processors incorporating the MPI library for parallelization. The complex flow field is analysed in detail using wall density, density gradient, vorticity, pressure, and enstrophy plots after validating the solver with the benchmark wall pressure, density, and v-velocity around the primary vortex provided by Zhou et al. (2018), Phys. Fluids, 30, 016102 for a Reynolds number 1000. It is observed that the triple point height and number of vortices in both separated zone and at the shear layer increase with an increase in Reynolds number. The grid-converged data obtained from the present simulation can be used as benchmark data to validate different numerical schemes/solvers at higher Reynolds numbers.

Computational Analysis of Fluid Forces on an Obstacle in a Channel Driven Cavity: Viscoplastic Material Based Characteristics.

In the current work, an investigation has been carried out for the Bingham fluid flow in a channel-driven cavity with a square obstacle installed near the inlet. A square cavity is placed in a channel to accomplish the desired results. The flow has been induced using a fully developed parabolic velocity at the inlet and Neumann condition at the outlet, with zero no-slip conditions given to the other boundaries. Three computational grids, C1, C2, and C3, are created by altering the position of an obstacle of square shape in the channel. Fundamental conservation and rheological law for viscoplastic Bingham fluids are enforced in mathematical modeling. Due to the complexity of the representative equations, an effective computing strategy based on the finite element approach is used. At an extra-fine level, a hybrid computational grid is created; a very refined level is used to obtain results with higher accuracy. The solution has been approximated using P2 − P1 elements based on the shape functions of the second and first-order polynomial polynomials. The parametric variables are ornamented against graphical trends. In addition, velocity, pressure plots, and line graphs have been provided for a better physical understanding of the situation Furthermore, the hydrodynamic benchmark quantities such as pressure drop, drag, and lift coefficients are assessed in a tabular manner around the external surface of the obstacle. The research predicts the effects of Bingham number (Bn) on the drag and lift coefficients on all three grids C1, C2, and C3, showing that the drag has lower values on the obstacle in the C2 grid compared with C1 and C3 for all values of Bn. Plug zone dominates in the channel downstream of the obstacle with augmentation in Bn, limiting the shear zone in the vicinity of the obstacle.

A novel adsorption differential volumetric apparatus to measure mass transfer in nanoporous materials

A novel adsorption differential volumetric apparatus was developed for the determination of diffusional time constants in nanoporous materials and applied to diffusion of nitrogen and argon in commercial pellets of 4A zeolite. The system is designed for high rates of data acquisition allowing to determine mass transfer time constants of seconds over the pressure range from vacuum to 130 kPa. Diffusion of N2 and Ar on a single pellet and fragments obtained from the pellet are studied between –10 °C and 35 °C and 0.8 to 55 kPa. These systems are chosen as representing weak adsorption to demonstrate the sensitivity of the apparatus that gives a good signal-to-noise ratio even with a single pellet in the entire pressure range. The systems studied confirm micropore diffusion control and an isothermal diffusion model was shown to reproduce accurately the observed kinetics using reduced pressure plots. As the crystal size in the pellet is not known accurately, the resulting activation energies and the ratio of diffusional time constants of N2 and Ar were used to validate the results against known literature values.

Computational Fluid Dynamic Analysis of Conceptual 3D Car Model

Abstract: From past decades, people are giving more attention to conservation of the fuels. The increasing number of passenger cars have increased the amount of traffic which directly impacts pollution and traffic congestion. Manufacturers are indulged into making lightweight and performance efficient automobiles. Implementation of different designs and materials has been in practice since ages. We need smaller vehicle designs for personal transport and electric vehicles to tackle the raising problems. In future designs, vehicles will be efficient enough to save more fuel and also the traffic problems may be solved. But for the design optimizations and experiments we need different analyses to be performed, one of which is aerodynamic analysis. In this paper a CFD analysis is done to check the aerodynamic performance of a proposed car design. The car has been designed using Onshape modeling software and analyzed in Simscale software. The car is subjected to different vehicle speeds and the results of drag coefficients and pressure plots are shown. Keywords: Design and analysis of a vehicle, CFD analysis, Aerodynamic analysis, 3D modelling, Drag coefficient, Pressure plot, Concept car, Performance Optimization.

Computational Fluid Dynamics (CFD) Analysis of 3D Car Model to Understanding Key Aerodynamic Issues and Their Interaction with Other Motorsport & Automotive Vehicle System

Abstract: Growing population of vehicles is one the biggest global concern and it led to traffic problems and creates congestion. People are not getting place to park their vehicles. Travel by car for shorter distance also stressful and time consuming because they have to face road traffic and usually cars are big at size so, to travel by car on road need more spacious and traffic free roads. that’s why some manufacturers start designing & manufacturing One seater vehicle which can easily transportable and create less congestion. If a single person wants to ride somewhere then he doesn’t have to take large car for one person, He can use single seater vehicle. In this assignment I have Designed and Tested a single seater electric vehicle which can easily transportable, compact and personal commuter vehicle (PMV). Keywords: CFD analysis, Aerodynamics analysis, automotive vehicle system, 3D modelling, pressure plot, performance optimization, vehicle aerodynamics.

Simulation of Internal Pipe Flows in Gasoline Port Fuel Injection System under Steady State Condition

Fluid flow models developed for pipe flows in gasoline port fuel injection system with different number of injectors working under steady state condition was simulated in this study using Flow Master Software. Using existing equations, theoretical analysis were computed for the same flow parameters and the results obtained for each parameter for both the simulation and theoretical approach were compared accordingly. The results obtained for theoretical approach and that of simulation had not shown much correlation due to the assumptions and computational errors. The pipe flow was simulated under steady state and the inlet pressure flowing across the circular pipe increased per unit time while fluctuations characterised by sinusoidal pattern were observed on the plot of total pressure at bends against time. The normal pressure while flowing along the pipe duct increased proportionally with the pipe length but suddenly experience a decline and picks up again as it encounters a bend. The mass flow rate of gasoline was observed to increases gradually as the simulation time progressed. For the three simulated outcomes, decrease were observed as the flow approaches bends along the circular pipe. Hence, the use of FLOWMASTER software in Computational Fluid Dynamics (CFDs) can help in predicting flow characteristics in hydraulic computations.

Raman spectroscopic study of cinnamyl-1 diphenylmethyl-4 piperazine (Cinnarizine) at high pressure

Raman spectra of Cinnarizine in the 35–3400 cm-1 region were studied at high pressures up to 15.3 GPa, using a Diamond Anvil Cell. Broadening of bands is observed starting from ∼0.9 up to ∼11–12 GPa pressures as evidenced by the changes in the Raman spectra of some modes. Plots of frequency vs pressure of bands, show increase of frequency with pressure for most of the bands and the slopes, dω/dP, of some bands show clear changes around ∼2.7, ∼5, ∼7.5 ∼9 and ∼11–12 GPa indicating phase transformation caused by changes in structure and chemical bonds at these pressures. The present article describes high pressure effects on cinnarizine studied by Raman Spectroscopy and is supported by density function theoretical calculations.

New Insights on Characteristics of the Near-Wellbore Fractured Zone from Simulated High-Resolution Distributed Strain Sensing Data

Summary Rayleigh frequency-shift-based distributed strain sensing (RFS-based DSS) is a fiber-optic-based diagnostic technique, which can measure the strain change along the fiber. The spatial resolution of RFS-based DSS can be as low as 0.2 m, and the measuring sensitivity is less than 1 με. Jin et al. (2021) presented a set of DSS data from the Hydraulic Fracture Test Site 2 project to demonstrate its potential to characterize near-wellbore fracture properties and to evaluate perforation efficiency during production and shut-in periods. Extensional strain changes are observed at locations around perforations during a shut-in period. At each perforation cluster, the observed responses of strain changes are significantly different. However, the driving mechanisms for the various observations are not clear, which hinders accurate interpretations of DSS data for near-wellbore fracture characterization. In this study, we applied a coupled flow and geomechanics model to simulate the observed DSS signals under various fractured reservoir conditions. The objective is to improve understanding of the DSS measurements and characterize near-wellbore fracture geometry. We used our in-house coupled flow and geomechanics simulator, which is developed by a combined finite-volume and finite-element method, to simulate strain responses within and near a fracture during shut-in and reopen periods. Local grid refinement was adopted around fractures and the wellbore, so that the simulated strain data can accurately represent the DSS measurements. The plane-strain condition is assumed. Numerical models with various fracture geometries and properties were constructed with representative parameters and in-situ conditions of the Permian Basin. The simulated well was shut-in for 4 days after producing 240 days, and reopened again for 1 day, following the actual field operation as shown in Jin et al. (2021). The characters of the strain changes along the fiber were analyzed and related to near-wellbore fracture properties. A novel diagnostic plot of relative strain change vs. wellbore pressure was presented to infer near-wellbore fracture characteristics. The impacts of permeability and size of the near-wellbore-stimulated region, fracture length, and near-perforation damage zone on strain responses were investigated through sensitivity analysis. The strain responses simulated by our model capture the observed signatures of field DSS measurements. During the shut-in period, clear positive strain changes are observed around the perforation locations, forming a “hump” signature. The shape of the “hump” region and peak value of each “hump” are dependent on the size and permeability of the near-wellbore fractured zone. Once the well is reopened, the strain changes decrease as the pressure drops. However, in one cycle of shut-in and reopen, the strain-pressure diagnostic plot shows path dependency. The discrepancy between the shut-in and reopen periods is highly influenced by the properties of near-wellbore fractured zones. The differences in the strain-pressure diagnostic plots can help to identify the conductive fractures. This study provides better understandings of the DSS measurements and their relations to the near-wellbore fracture properties, which is of practical importance for near-wellbore fracture characterization and completion/stimulation optimization.

Pressure and Pressure Derivative Interpretation of a Well in a Completed-Perforated Multilayer Reservoir with Crossflow

Several models have been introduced for the characterization of multilayer reservoirs. However, some have failed to provide results when the skin factor of the layers is negative. Therefore, in this work, a model applying the concept of the maximum effective hole diameter has been used to simulate pressure tests in multilayer reservoirs. The pressure behavior of such systems is similar to that of naturally fractured double porosity reservoirs. Then, using the unique features of the log–log plot of pressure and pressure derivative versus time, some expressions have been developed to characterize the reservoir. The equations are satisfactorily tested on three field examples.

Thermodynamics of germanium chemical vapor deposition via germane and digermane

Chemical vapor deposition is notoriously a challenging chemical process. Growth rates are stated either under mass-transfer control or under kinetic control at lower temperature. But a few drastic assumptions enable a radical simplification of the reaction mechanism. And both growth regimes are unified with Sedgwick’s simplified thermodynamic model. Linear functions of temperature akin to Gibbs free energy of reaction are mined out of germanium deposition experiments. Two growth mechanisms are identified, one with ΔHro = 83.4 kcal/mol (Ge–H bond) and a second one with ΔHro = 104.2 kcal/mol (H – H bond). The contribution of higher order germane is also discerned in germane thermal decomposition. The square root coupling of growth rates to input flows is neatly demonstrated with thermodynamics. Finally, chemical vapor deposition growth rate vs. precursor partial pressure plot fingerprints a hydrogen Langmuir adsorption isotherm. The adsorption isotherm reveals a thermodynamic contribution beneath a mass-transfer control.

Effect of flap deflection angle on flow characteristics of aerofoil

A wing is used in aircraft to employ lift based on the fundamental principle of aerodynamics. The cross-section of a wing gives the aerofoil shape, and thus investigation of flow characteristics of aerofoil is important to understand the lift and drag mechanisms in wing. Flaps are the components using in the wings to generate additional lift and drag when required. While aircraft take-off, flaps help in generating addition lift, and while in landing, they do aerodynamic braking. Therefore, flaps play an important role in aircraft. The present paper investigates the angle of flaps on flow characteristics in NACA 4415 aerofoil using XFoil software. The variations obtained showed notable variations in the coefficient of pressure (Cp) plots. The various aerodynamic coefficients such as lift and drag coefficients, and viscous pressure distribution were obtained corresponding to the flap deflection angle. From the results, for flap angles above 0o, the aerofoil can generate a “sudden” lift which is useful in take-off conditions. While the flap angles are made below zero degrees, the lift is observed to decrease contributing to more drag. Polar plots are made to summarize and visualize the above results graphically.

A Numerical Investigation of Turbulent Flow Over Single and Tandem Square Cylinders

This paper presents the three-dimensional flow investigations over the square cylinders placed in the tandem arrangement. Two different flow configurations were investigated in detail; one comprising of a single square cylinder and the other comprising of three square cylinders placed in a tandem arrangement with the spacing of six times the width (w) of each square cylinder. The Reynolds number based on the width of the square cylinder (w) and free stream velocity (Uo) is 22,000. The problem was solved numerically using an Unsteady Reynolds-Averaged Navier-Stokes (URANS) based model and Large Eddy Simulation (LES) based model. Strouhal Number, lift, and drag coefficients were computed for each configuration. By comparing both the models using contour plots of pressure, velocity and vorticity it is found that the LES model is more accurate to capture the turbulence around single and tandem square cylinders. In the tandem arrangement, complex periodic vortex shedding was observed in the wake of each square cylinder. The production of turbulent kinetic energy was also investigated to understand the roles of stresses during flow over the cylinders. The analysis showed that the production of turbulence by normal stresses is higher than that of shear stresses. Furthermore, it was observed that the flow over the first cylinder arranged in tandem is quite identical to that of the single square cylinder. Moreover, the upstream cylinder experienced a higher lift in comparison to the downstream cylinders.