scholarly journals Jet Oscillation Frequency Characterization of a Sweeping Jet Actuator

Fluids ◽  
2020 ◽  
Vol 5 (2) ◽  
pp. 72
Author(s):  
Furkan Oz ◽  
Kursat Kara
Keyword(s):  
Mach Number ◽  
Oscillation Frequency ◽  
Compressible Flows ◽  
Three Dimensional ◽  
Computational Domain ◽  
Time Resolved ◽  
Average Value ◽  
Exit Nozzle ◽  
Oscillating Jet ◽  
Jet Oscillation

The time-resolved flow field of a spatially oscillating jet emitted by a sweeping jet (SWJ) actuator is investigated numerically using three-dimensional Reynolds-averaged Navier–Stokes (3D-URANS) equations. Numerical simulations are performed for a range of mass flow rates providing flow conditions varying from incompressible to subsonic compressible flows. After a detailed mesh study, the computational domain is represented using two million hexagonal control volumes. The jet oscillation frequency is predicted by analyzing velocity time histories at the actuator exit, and a linear relationship between the jet oscillation frequency and time-averaged exit nozzle Mach number is found ( f = 511.22   M + 46.618 , R² = 0.97). The results of our numerical model are compared with data from the literature, and a good agreement is found. In addition, we confirmed that the Strouhal number is almost constant with the Mach number for the subsonic oscillating jet and has an average value of St = 0.0131. The 3D-URANS model that we presented here provides a computationally inexpensive yet accurate alternative to the researchers to investigate jet oscillation characteristics.

scholarly journals Jet Oscillation Frequency Characterization of a Sweeping Jet Actuator

2020 ◽  
Author(s):  
Furkan Oz ◽  
Kursat Kara
Keyword(s):  
Mass Flow ◽  
Oscillation Frequency ◽  
Compressible Flows ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Time Resolved ◽  
Linear Mode ◽  
Oscillating Jet ◽  
Mass Flow Rates ◽  
Jet Oscillation

The time-resolved flowfield of a spatially oscillating jet emitted by a Sweeping Jet (SWJ) actuator is investigated numerically using three-dimensional Reynolds-averaged Navier-Stokes (3D-URANS) equations. Numerical simulations are performed for a practical range of mass flow rates providing flow conditions ranging from incompressible to subsonic compressible flows. A linear relationship between the mass flow rate and the jet oscillation frequency is found. The results of the numerical model are compared with the experimental data in the literature, and good agreement is found. Additionally, it is observed that the SWJ actuator frequency response switches from one linear mode to another linear mode when the compressibility effects become important.

scholarly journals Theory, Analysis, and Applications of the Entropic Lattice Boltzmann Model for Compressible Flows

Entropy ◽  
2020 ◽  
Vol 22 (3) ◽  
pp. 370 ◽  
Author(s):  
Nicolò Frapolli ◽  
Shyam Chikatamarla ◽  
Ilya Karlin
Keyword(s):  
Mach Number ◽  
Supersonic Flow ◽  
Flow Field ◽  
Lattice Boltzmann ◽  
Compressible Flows ◽  
Three Dimensional ◽  
Lattice Boltzmann Model ◽  
Temperature Range ◽  
Naca0012 Airfoil ◽  
New Construction

The entropic lattice Boltzmann method for the simulation of compressible flows is studied in detail and new opportunities for extending operating range are explored. We address limitations on the maximum Mach number and temperature range allowed for a given lattice. Solutions to both these problems are presented by modifying the original lattices without increasing the number of discrete velocities and without altering the numerical algorithm. In order to increase the Mach number, we employ shifted lattices while the magnitude of lattice speeds is increased in order to extend the temperature range. Accuracy and efficiency of the shifted lattices are demonstrated with simulations of the supersonic flow field around a diamond-shaped and NACA0012 airfoil, the subsonic, transonic, and supersonic flow field around the Busemann biplane, and the interaction of vortices with a planar shock wave. For the lattices with extended temperature range, the model is validated with the simulation of the Richtmyer–Meshkov instability. We also discuss some key ideas of how to reduce the number of discrete speeds in three-dimensional simulations by pruning of the higher-order lattices, and introduce a new construction of the corresponding guided equilibrium by entropy minimization.

Numerical Simulation of the Aerodynamic Behavior of Propeller Blades at Subsonic Conditions

2012 ◽  
Author(s):  
Mohamed B. Farghaly ◽  
Ahmed F. El-Sayed ◽  
Galal B. Salem
Keyword(s):  
Mach Number ◽  
Control Volume ◽  
Three Dimensional ◽  
Power Coefficient ◽  
Detailed Knowledge ◽  
Computational Domain ◽  
Thrust Coefficient ◽  
Oil Crisis ◽  
Propeller Blades ◽  
Control Volume Approach

The Organization of the Petroleum Exporting Countries (OPEC) oil crisis of the mid 1970s led to a revival in interest in the propeller as a possible fuel-efficient propulsion for aircraft operating at subsonic cruise speeds. A propeller aerodynamics is complex and should be analyzed carefully to ensure maximum propellers efficiency. Detailed knowledge of flow patterns and aerodynamics loads is necessary for blade material and manufacturing process. In this study, an isolated propeller blade is chosen as the base of analysis, the geometry of the propeller: twist and chord variation with radius, are taken from real case module. The boundary conditions of the computational domain are set corresponding to that exist in the propeller manuals. A three dimensional unstructured grid was generated and adopted using commercial grid generator GAMBIT software. The governing equations are solved using FLUENT6.3.26 a commercial CFD code, which uses a control volume approach on a grid over the computational domain. Results identified that the propeller efficiency, power coefficient are increases to reach maximum values and then decreases with increase Mach number. The thrust coefficient decreases with increase Mach number.

scholarly journals Picosecond time-resolved photon antibunching measures nanoscale exciton motion and the true number of chromophores

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Gordon J. Hedley ◽  
Tim Schröder ◽  
Florian Steiner ◽  
Theresa Eder ◽  
Felix J. Hofmann ◽  
...  
Keyword(s):  
Rational Design ◽  
Three Dimensional ◽  
Dna Origami ◽  
Fluorescent Nanoparticles ◽  
Time Resolved ◽  
Exciton Diffusion ◽  
Polymer Aggregates ◽  
True Number ◽  
Particle Level ◽  
Photon Antibunching

AbstractThe particle-like nature of light becomes evident in the photon statistics of fluorescence from single quantum systems as photon antibunching. In multichromophoric systems, exciton diffusion and subsequent annihilation occurs. These processes also yield photon antibunching but cannot be interpreted reliably. Here we develop picosecond time-resolved antibunching to identify and decode such processes. We use this method to measure the true number of chromophores on well-defined multichromophoric DNA-origami structures, and precisely determine the distance-dependent rates of annihilation between excitons. Further, this allows us to measure exciton diffusion in mesoscopic H- and J-type conjugated-polymer aggregates. We distinguish between one-dimensional intra-chain and three-dimensional inter-chain exciton diffusion at different times after excitation and determine the disorder-dependent diffusion lengths. Our method provides a powerful lens through which excitons can be studied at the single-particle level, enabling the rational design of improved excitonic probes such as ultra-bright fluorescent nanoparticles and materials for optoelectronic devices.

scholarly journals Data-Informed Decomposition for Localized Uncertainty Quantification of Dynamical Systems

Vibration ◽  
2020 ◽  
Vol 4 (1) ◽  
pp. 49-63
Author(s):  
Waad Subber ◽  
Sayan Ghosh ◽  
Piyush Pandita ◽  
Yiming Zhang ◽  
Liping Wang
Keyword(s):  
Dynamical Systems ◽  
Computational Cost ◽  
Three Dimensional ◽  
Region Of Interest ◽  
System Response ◽  
Computational Domain ◽  
User Interest ◽  
Numerical Resolution ◽  
Multi Scale ◽  
Operation Conditions

Industrial dynamical systems often exhibit multi-scale responses due to material heterogeneity and complex operation conditions. The smallest length-scale of the systems dynamics controls the numerical resolution required to resolve the embedded physics. In practice however, high numerical resolution is only required in a confined region of the domain where fast dynamics or localized material variability is exhibited, whereas a coarser discretization can be sufficient in the rest majority of the domain. Partitioning the complex dynamical system into smaller easier-to-solve problems based on the localized dynamics and material variability can reduce the overall computational cost. The region of interest can be specified based on the localized features of the solution, user interest, and correlation length of the material properties. For problems where a region of interest is not evident, Bayesian inference can provide a feasible solution. In this work, we employ a Bayesian framework to update the prior knowledge of the localized region of interest using measurements of the system response. Once, the region of interest is identified, the localized uncertainty is propagate forward through the computational domain. We demonstrate our framework using numerical experiments on a three-dimensional elastodynamic problem.

scholarly journals The Numerical Analysis of the Flow on the Smooth and Nonsmooth Boundaries by IBEM/DBIEM

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Gang Xu ◽  
Guangwei Zhao ◽  
Jing Chen ◽  
Shuqi Wang ◽  
Weichao Shi
Keyword(s):  
Boundary Value ◽  
Three Dimensional ◽  
Boundary Surface ◽  
Tangential Velocity ◽  
Integral Equation Method ◽  
Boundary Integral ◽  
Surface Shape ◽  
Normal Vector ◽  
Computational Domain ◽  
Nonsmooth Boundary

The value of the tangential velocity on the Boundary Value Problem (BVP) is inaccurate when comparing the results with analytical solutions by Indirect Boundary Element Method (IBEM), especially at the intersection region where the normal vector is changing rapidly (named nonsmooth boundary). In this study, the singularity of the BVP, which is directly arranged in the center of the surface of the fluid computing domain, is moved outside the computational domain by using the Desingularized Boundary Integral Equation Method (DBIEM). In order to analyze the accuracy of the IBEM/DBIEM and validate the above-mentioned problem, three-dimensional uniform flow over a sphere has been presented. The convergent study of the presented model has been investigated, including desingularized distance in the DBIEM. Then, the numerical results were compared with the analytical solution. It was found that the accuracy of velocity distribution in the flow field has been greatly improved at the intersection region, which has suddenly changed the boundary surface shape of the fluid domain. The conclusions can guide the study on the flow over nonsmooth boundaries by using boundary value method.

Investigation of the 3D Unsteady Rotor Pressure Field in a HP Turbine Stage

2002 ◽  
Author(s):  
E. Valenti ◽  
J. Halama ◽  
R. De´nos ◽  
T. Arts
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Pressure Field ◽  
Pressure Ratio ◽  
Turbine Stage ◽  
Time Resolved ◽  
Mach Number Distribution ◽  
Rotor Surface ◽  
Exit Mach Number ◽  
Unsteady Pressure Measurements

This paper presents steady and unsteady pressure measurements at three span locations (15, 50 and 85%) on the rotor surface of a transonic turbine stage. The data are compared with the results of a 3D unsteady Euler stage calculation. The overall agreement between the measurements and the prediction is satisfactory. The effects of pressure ratio and Reynolds number are discussed. The rotor time-averaged Mach number distribution is very sensitive to the pressure ratio of the stage since the incidence of the flow changes as well as the rotor exit Mach number. The time-resolved pressure field is dominated by the vane trailing edge shock waves. The incidence and intensity of the shock strongly varies from hub to tip due to the radial equilibrium of the flow at the vane exit. The decrease of the pressure ratio attenuates significantly the amplitude of the fluctuations. An increase of the pressure ratio has less significant effect since the change in the vane exit Mach number is small. The effect of the Reynolds number is weak for both the time-averaged and the time-resolved rotor static pressure at mid-span, while it causes an increase of the pressure amplitudes at the two other spans.

scholarly journals Computational Analysis to Factor Wind into the Design of an Architectural Environment

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Hassam Nasarullah Chaudhry ◽  
John Kaiser Calautit ◽  
Ben Richard Hughes
Keyword(s):  
Fluid Dynamics ◽  
Power Generation ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Numerical Data ◽  
Navier Stokes ◽  
Windward Side ◽  
Average Value ◽  
Continuity Equations ◽  
Prevailing Wind Direction

The effect of wind distribution on the architectural domain of the Bahrain Trade Centre was numerically analysed using computational fluid dynamics (CFD). Using the numerical data, the power generation potential of the building-integrated wind turbines was determined in response to the prevailing wind direction. The three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations along with the momentum and continuity equations were solved for obtaining the velocity and pressure field. Simulating a reference wind speed of 6 m/s, the findings from the study quantified an estimate power generation of 6.4 kW indicating a capacity factor of 2.9% for the benchmark model. At the windward side of the building, it was observed that the layers of turbulence intensified in inverse proportion to the height of the building with an average value of 0.45 J/kg. The air velocity was found to gradually increase in direct proportion to the elevation with the turbine located at higher altitude receiving maximum exposure to incoming wind. This work highlighted the potential of using advanced computational fluid dynamics in order to factor wind into the design of any architectural environment.

Impact of an Aortic Nitinol Stent Graft on Flow Measurements by Time-resolved Three-dimensional Velocity-encoded MRI

2012 ◽  
Vol 19 (3) ◽  
pp. 274-280 ◽  
Author(s):  
Fabian Rengier ◽  
Michael Delles ◽  
Roland Unterhinninghofen ◽  
Sebastian Ley ◽  
Sasan Partovi ◽  
...  
Keyword(s):  
Stent Graft ◽  
Three Dimensional ◽  
Flow Measurements ◽  
Time Resolved ◽  
Nitinol Stent
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