Characteristics of a Single Sensor Fiber-Coupled 3D PIV for Reacting Flow-Fields

2021 ◽  
Author(s):  
Cal Rising ◽  
Jonathan Reyes ◽  
Kareem Ahmed
Keyword(s):  
High Speed ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Flow Fields ◽  
Velocity Fields ◽  
Diagnostic Approach ◽  
Reacting Flow ◽  
Shear Stresses ◽  
Piv Measurement ◽  
Single Sensor

Abstract Tomographic particle image velocimetry (Tomo-PIV) has become a standard tool for capturing a three-dimensional velocity fields in non-reacting flows. However, the diagnostic approach can become costly and challenging to implement when extended to applications which require high-speed cameras. This limitation has led to the use of fiber wound bundles to allow for multiple views to be captured on a single camera sensor. Additionally, employing this diagnostic approach on reacting flow fields becomes more complex as the introduction of the flame causes additional luminosity and optical distortion which impacts the particle field reconstruction. The current work seeks to validate and determine the limitations when utilizing a single sensor fiber coupled approach for capturing Tomo-PIV data on a reacting flow-field. A premixed propane (C3H8) and air Bunsen burner flame is utilized to examine if the single sensor approach can meet the parameters for acceptable reconstruction based on previous research. The resulting velocity fields are then compared to a traditional PIV measurement to assess the deviation of the single sensor approach from a standard velocimetry measurement approach. It is demonstrated that there is strong agreement between the velocity and vorticity for the average flow-fields, however when comparing the Reynolds Shear Stresses a significant deviation is revealed. The deviation is attributed to strong velocity fluctuations occurring within the instantaneous Tomo-PIV data, which creates a significant divergence between the measurement techniques on an instantaneous basis. This demonstrates that while the approach can obtain reliable velocity and vorticity statistics, there is significant limitations in calculating second-order turbulence statistics. Thus, revealing that there is a tradeoff between the ability to extract the full velocity gradient tensor and the extent of the turbulence related analysis which can be reliably performed.

An Accurate Performance Prediction of Solid Fuel Ramjets Using Coupled Intake-Combustor-Nozzle Simulation

2020 ◽  
Vol 36 (6) ◽  
pp. 933-941
Author(s):  
A. M. Tahsini
Keyword(s):  
Combustion Chamber ◽  
Solid Fuel ◽  
Solid Phase ◽  
Three Dimensional ◽  
Flow Fields ◽  
Reacting Flow ◽  
Computational Domain ◽  
Regression Rate ◽  
Fuel Flow ◽  
Accurate Performance

ABSTRACTThe performance of the solid fuel ramjet is accurately predicted using full part simulation of this propulsion system, where the flow fields of the intake, combustion chamber, and the nozzle are numerically studied all together. The conjugate heat transfer is considered between the solid phase and the gas phase to directly compute the regression rate of the fuel. The finite volume solver of the compressible turbulent reacting flow is utilized to study the axisymmetric three dimensional flow fields, and two blocks are used to discretize the computational domain. It is shown that the combustion chamber's pressure is changed due to the fuel flow rate's increment which must be taken into account in predictions. The results demonstrate that omitting the pressure dependence of the regression rate and also the effect of the combustor's inlet profile on the regression rate, which specially exists when simulating the combustion chamber individually, under-predicts the solid fuel burning rate when the regression rate augmentation technique is applied to improve the performance of the solid fuel ramjets. It is also illustrated that using the inlet swirl to increase the regression rate of the solid fuel augments considerably the thrust level of the considered SFRJ, while the predictions without considering all parts of the ramjet is not accurate.

scholarly journals Tomographic particle image velocimetry of desert locust wakes: instantaneous volumes combine to reveal hidden vortex elements and rapid wake deformation

2012 ◽  
Vol 9 (77) ◽  
pp. 3378-3386 ◽  
Author(s):  
Richard J. Bomphrey ◽  
Per Henningsson ◽  
Dirk Michaelis ◽  
David Hollis
Keyword(s):  
Particle Image Velocimetry ◽  
High Speed ◽  
Particle Image ◽  
Aerodynamic Force ◽  
Three Dimensional ◽  
Flow Fields ◽  
Diagnostic Methods ◽  
Tomographic Particle Image Velocimetry ◽  
Image Velocimetry ◽  
Spatio Temporal

Aerodynamic structures generated by animals in flight are unstable and complex. Recent progress in quantitative flow visualization has advanced our understanding of animal aerodynamics, but measurements have hitherto been limited to flow velocities at a plane through the wake. We applied an emergent, high-speed, volumetric fluid imaging technique (tomographic particle image velocimetry) to examine segments of the wake of desert locusts, capturing fully three-dimensional instantaneous flow fields. We used those flow fields to characterize the aerodynamic footprint in unprecedented detail and revealed previously unseen wake elements that would have gone undetected by two-dimensional or stereo-imaging technology. Vortex iso-surface topographies show the spatio-temporal signature of aerodynamic force generation manifest in the wake of locusts, and expose the extent to which animal wakes can deform, potentially leading to unreliable calculations of lift and thrust when using conventional diagnostic methods. We discuss implications for experimental design and analysis as volumetric flow imaging becomes more widespread.

scholarly journals Velocity and stress fields in grounded glaciers: a simple algorithm for including deviatoric stress gradients

1995 ◽  
Vol 41 (138) ◽  
pp. 333-344 ◽  
Author(s):  
Heinz Blatter
Keyword(s):  
Method Of Lines ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Velocity Fields ◽  
Deviatoric Stress ◽  
Shear Stresses ◽  
Algebraic Equations ◽  
Field Equations ◽  
Stress Gradients ◽  
The Method Of Lines

AbstractA new and efficient algorithm for computing the three-dimensional stress and velocity fields in grounded glaciers includes the role of deviatoric stress gradients. A consistent approximation of first order in the aspect of ratio of the ice mass gives a set of eight field equations for the five stress and three velocity components and the corresponding boundary conditions. A coordinate transformation mapping the local ice thickness on to unity and approximating the derivatives in the horizontal direction by centered finite-differences yields five ordinary differential and three algebraic equations. This allows use of the method of lines, starting the integration with prescribed stress and velocity components at the base, and a simple iteration procedure converges rapidly.The algorithm can be used for a wide rangе of stress-strain-rate relations, as long as strain only depends on deviatoric and shear stresses and on temperature. Sensitivity tests using synthetic and realistic ice geometries show the relevance of normal deviatoric stresses in the solutions for the velocity components even for ice sheets. Stress and velocity fields may deviate substantially from the widely used shallow-ice approximation.

Numerical Analysis of Aeroacoustic Noise for High-Speed Face Milling Cutters in Three Dimensional Unsteady Flow Fields

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Chunhui Ji ◽  
Zhanqiang Liu
Keyword(s):  
High Speed ◽  
Reference Frames ◽  
Acoustic Noise ◽  
Environmental Concern ◽  
Three Dimensional ◽  
Vertical Plane ◽  
Flow Fields ◽  
Face Milling ◽  
Noise Generation ◽  
Aeroacoustic Noise

Aeroacoustic noise produced by high speed face milling cutters is a serious environmental concern. This paper develops a modeling approach to investigate the aeroacoustic noise generation and propagation by the idling face milling cutters. The approach consists of two parts: (1) an aerodynamic model for evaluating the flow fields based on the Navier–Stokes (N–S) equation and (2) an aeroacoustic model for predicting the acoustic noise by using the Ffowcs Williams and Hawkings (FW–H) equation. Both the steady mode with the multiple reference frames (MRF) model and the unsteady mode with the sliding mesh technique by introducing steady flow variables as its initial fields are simulated. The cutter gullet regions and the insert rake face regions are found to be the primary contributors in noise generation through spectral analysis of noise sources. The acoustic noise in face milling is significantly affected by the cutter diameter and the number of cutter teeth. The noise directivity is found in vertical plane, and the irregular tooth spacing can spread the maximum sound power at the rotating frequency to higher frequencies. In addition, experiments are conducted to measure the acoustic noise from two high speed milling cutters. It is found that the experimental results are generally in good agreement with the simulations.

Experimental Flow Studies in Exact-Replica Phantoms of Atherosclerotic Carotid Bifurcations Under Steady Input Conditions

2003 ◽  
Vol 125 (1) ◽  
pp. 38-48 ◽  
Author(s):  
J. Bale-Glickman ◽  
K. Selby ◽  
D. Saloner ◽  
O¨. Savas¸
Keyword(s):  
Three Dimensional ◽  
Carotid Bifurcation ◽  
Reynolds Numbers ◽  
Flow Fields ◽  
Shear Stresses ◽  
Treatment Technique ◽  
Input Flow ◽  
Stagnation Points ◽  
Topological Features ◽  
Recirculation Zones

Extensive flow studies are conducted in two carotid bifurcation flow phantoms. These phantoms exactly replicate the lumen of the plaque excised intact from two patients with severe carotid atherosclerosis. The input flow into the phantom’s common carotid artery is steady. Novel scanning techniques for flow visualization and particle image velocimetry are used. In addition, a novel boundary treatment technique is employed in velocimetry to extract first order accurate velocity gradients at walls. The data show that the flow fields are highly three-dimensional. Numerous separation and recirculation zones dominate the flow domain, except at the lowest Reynolds numbers. The separation regions are often so severe that highly directed internal jets form. At high Reynolds numbers, the flows become unsteady and chaotic, even though the input flow is steady. Flow fields have large regions of energetic flow and almost stagnant recirculation zones. These recirculation zones range in size from the full size of the arteries to zones within crevasses smaller than 1 mm. Velocity field and streamline patterns conform well to the lumen geometry. The streamlines are highly tortuous. Stagnation points correlate well with the topological features of the stenosis. Vorticity maps confirm the highly complex and three dimensional nature of the flow. Wall shear stresses at the stenoses are estimated to be on the order of 10 Pa. These studies conclusively show that the nature of the flow in the diseased bifurcation is primarily dictated by the lumen geometry.

A Mass Conservative Streamline Tracking Method for Three Dimensional CFD Velocity Fields

2003 ◽  
Author(s):  
Zhenquan Li
Keyword(s):  
Incompressible Flows ◽  
Three Dimensional ◽  
Mass Conservation ◽  
Flow Fields ◽  
Construction Method ◽  
Velocity Fields ◽  
Three Dimensions ◽  
Linear Mass ◽  
Tracking Method

Mass conservation is a key issue for accurate streamline visualization of flow fields. This paper presents a mass conservative streamline construction method for CFD velocity fields defined at discrete locations in three dimensions for incompressible flows. Linear mass conservative interpolation is used to approximate velocity fields. Demonstration examples are shown.

scholarly journals Experimental Two-Phase Flow Analysis Inside a Laboratory Scale Jet-Engine Combustion Chamber Using PIV

2020 ◽  
Author(s):  
Thomas von Langenthal ◽  
Nikolaos Zarzalis ◽  
Alexandra Loukou
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Velocity Field ◽  
Cross Correlation ◽  
Measurement Techniques ◽  
Flow Fields ◽  
Velocity Fields ◽  
Phase Flow ◽  
Two Phase ◽  
Aero Engine

Abstract The characterization of the two-phase kerosene/air flow near the nozzle of an aero engine combustor is important in order to understand the combustion characteristics of the burner. Typically, Particle Image Velocimetry (PIV) or Laser Doppler Velocimetry (LDV) is used to measure velocities inside aero engine combustors. However, these measurement techniques rely on tracer particles to visualize the flow field and are usually only able to measure the velocity field of one phase at a time. In the case of PIV measurements both the flow tracers and the kerosene droplets scatter the laser light and thus, appear on the PIV recordings. Depending on droplet size and flow velocity, these kerosene droplets do not necessarily follow the airflow leading to errors in the derived velocity field. This work presents a method on how to separate kerosene droplets from flow tracers depending on their optical characteristics in the PIV recording. This phase separation enables the independent measurement of the flow fields of both the gaseous and liquid phase at the same time using a standard PIV setup. The method is demonstrated on a laboratory scale aero engine combustor operated at atmospheric conditions. The test rig features liquid kerosene combustion with realistic inlet temperatures and pressure drop as well as good access for optical measurement techniques. The phases are separated by filtering the images with noise reduction filters for suppressing the signal of the flow tracers, and edge detection filters to detect the kerosene droplets. The detected kerosene droplets are removed from the PIV pictures and the pictures are evaluated using standard PIV cross-correlation. Afterwards the liquid phase images are evaluated using Particle Tracking Velocimetry (PTV). This phase separation can lead to errors in the derived velocity fields because of incorrect and incomplete particle detection or due to errors in the cross correlation at the edges of detected particles. These errors in the phase separation are quantified by evaluating artificial two-phase flow PIV pictures with similar optical properties to the actual two-phase PIV pictures, and comparing the derived velocity fields to the results calculated using the original, unaltered pictures. The obtained results show, that in the setup under investigation, gaseous and liquid phase can have significantly different flow fields with kerosene droplets moving in the opposite direction of the recirculating airflow. The influence of essential parameters like seeding and spray density are discussed and at positions with a sufficient data rate, the instantaneous slip velocity between droplets and gaseous flow is calculated. Generally, the presented method appears to be suitable for studying combustion with liquid kerosene injection.

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