scholarly journals Three-dimensional density measurements of a heated jet using laser-speckle tomographic background-oriented schlieren

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Shoaib Amjad ◽  
Julio Soria ◽  
Callum Atkinson
Keyword(s):  
Refractive Index ◽  
Turbulent Flows ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Density Field ◽  
Laser Speckle ◽  
Spatial Density ◽  
Reference Image ◽  
Mixing Processes ◽  
Background Oriented Schlieren

Three-dimensional density field measurement techniques can be used to understand the complex heat transfer and mixing processes that occur in turbulent flows. Tomographic background-oriented schlieren (BOS) is an optical technique that can be used to measure the instantaneous three-dimensional density field in turbulent flows. Light rays propagating through the flow are deflected from their ambient path due to variations in refractive index related to the spatial density gradients. In BOS, a camera is placed looking through the flow at a reference image, which captures path-integrated information on the refractive index gradients in the form of apparent image displacements Richard and Raffel (2001). The displacements recorded simultaneously from many cameras placed around the flow form the basis of a tomographic reconstruction of the three-dimensional refractive index gradients Goldhahn and Seume (2007), from which the density field is obtained through integration of the gradients and application of the Gladstone-Dale relation.

scholarly journals Three-Dimensional Numerical Simulation and Performance Study of an Industrial Helical Static Mixer

2005 ◽  
Vol 127 (3) ◽  
pp. 467-483 ◽  
Author(s):  
Ramin K. Rahmani ◽  
Theo G. Keith ◽  
Anahita Ayasoufi
Keyword(s):  
Turbulent Flow ◽  
Turbulent Flows ◽  
Stokes Equations ◽  
Critical Role ◽  
Three Dimensional ◽  
Static Mixer ◽  
Performance Study ◽  
Mixing Processes ◽  
Viscous Liquids ◽  
Wide Range

In many branches of processing industries, viscous liquids need to be homogenized in continuous operations. Consequently, fluid mixing plays a critical role in the success or failure of these processes. Static mixers have been utilized over a wide range of applications such as continuous mixing, blending, heat and mass transfer processes, chemical reactions, etc. This paper describes how static mixing processes of single-phase viscous liquids can be simulated numerically, presents the flow pattern through a helical static mixer, and provides useful information that can be extracted from the simulation results. The three-dimensional finite volume computational fluid dynamics code used here solves the Navier-Stokes equations for both laminar and turbulent flow cases. The turbulent flow cases were solved using k-ω model and Reynolds stress model (RSM). The flow properties are calculated and the static mixer performance for different Reynolds numbers (from creeping flows to turbulent flows) is studied. A new parameter is introduced to measure the degree of mixing quantitatively. Furthermore, the results obtained by k-ω and RSM turbulence models and various numerical details of each model are compared. The calculated pressure drop is in good agreement with existing experimental data.

Magnetic Resonance Thermometry Experimental Setup: A Portable Heat Transfer Experiment

2016 ◽  
Author(s):  
Elliott T. Williams ◽  
Jonathan R. Spirnak ◽  
Marc C. Samland ◽  
Brant G. Tremont ◽  
Alfred L. McQuirter ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Turbulent Flows ◽  
Imaging System ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Cross Flow ◽  
Experimental Setup ◽  
Magnetic Resonance Imaging System ◽  
Magnetic Resonance Thermometry ◽  
Jet Mixing

This work provides a detailed description of the setup and execution of an experiment employing Magnetic Resonance Thermometry (MRT) techniques for measuring the three-dimensional temperature field of a fully turbulent jet mixing with a cross flow. The proposed methodology has the flexibility of applying different thermal boundary conditions — adiabatic and conductive — by varying the materials used in the test section as well as varying the temperatures of the mixing flows. The experiment described in this paper employs a standard magnetic resonance imaging system comparable to those used in medical radiology departments worldwide. A series of MR scans with both isothermal and thermal mixing conditions were conducted and results are presented with sub-millimeter resolution across the measured 3D domain of interest within one degree Celsius. The methodology presented here holds unique advantages over conventional techniques because measurements can be acquired without introducing flow disturbances and in regions without any optical access. When coupled with other established MR-based measurement techniques, MRT provides large, robust data sets that can be used for validation, design, and insight into system thermal performance for complex, turbulent flows. The materials and components employed in this work cost approximately $13,900, and the experimental setup and data collection required approximately 48 hours.

scholarly journals Mobile visualization of density fields using smartphone background-oriented schlieren

2019 ◽  
Vol 60 (11) ◽  
Author(s):  
Keisuke Hayasaka ◽  
Yoshiyuki Tagawa
Keyword(s):  
Density Gradient ◽  
High Speed ◽  
Density Field ◽  
Gradient Field ◽  
Reference Image ◽  
Target Image ◽  
High Speed Imaging ◽  
Time Step ◽  
Background Oriented Schlieren ◽  
Background Image

Abstract The conventional background-oriented schlieren (BOS) technique is an image-based technique that can calculate the density field in fluids using two static images [i.e., an undistorted background image (reference image) and a distorted background image due to the density change in fluids (target image)]. This paper proposes the smartphone BOS (SBOS) technique, which offers the measurement of the density gradient using the high-speed imaging feature of the smartphone being carried with a moving observer. The conventional BOS with a fixed camera visualizes the density gradient by comparing the reference image and the target image. In contrast, SBOS can obtain the time difference of the density gradient field. A reference image in SBOS is a target one at a previous time step. The movement of the smartphone is canceled using a registration technique for image accurate alignment. Three demonstrations are conducted to perform SBOS. First, in a static situation, the density field of heated air by a gas burner is visualized by comparing between SBOS and conventional BOS. Second, the local displacement of density field and the error displacement is estimated quantitatively when the smartphone is moving. Third, SBOS using an embossed wallpaper to visualize the density field is performed in the mobile condition. These achievements suggest that SBOS is an effective system to visualize the density field using only the smartphone, and is expected to be a useful tool such as a preliminary experiment in the laboratory and a teaching tool for general smartphone users.

Reconstruction of Objects from their Projections Using Orthogonal Functions

1973 ◽  
Vol 31 ◽  
pp. 268-269
Author(s):  
Elrnar Zeitler
Keyword(s):  
Unit Area ◽  
Three Dimensional ◽  
One Dimension ◽  
Spatial Density ◽  
Dimensional Representation ◽  
Orthogonal Functions ◽  
Object A ◽  
Plane Normal ◽  
Dimensional Object ◽  
Spatial Density Distribution

Considering any finite three-dimensional object, a “projection” is here defined as a two-dimensional representation of the object's mass per unit area on a plane normal to a given projection axis, here taken as they-axis. Since the object can be seen as being built from parallel, thin slices, the relation between object structure and its projection can be reduced by one dimension. It is assumed that an electron microscope equipped with a tilting stage records the projectionWhere the object has a spatial density distribution p(r,ϕ) within a limiting radius taken to be unity, and the stage is tilted by an angle 9 with respect to the x-axis of the recording plane.

scholarly journals Numerical Study of Three-Dimensional Surface Jets Emerging from a Fishway Entrance Slot

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1079
Author(s):  
Lena Mahl ◽  
Patrick Heneka ◽  
Martin Henning ◽  
Roman B. Weichert
Keyword(s):  
Boundary Conditions ◽  
Turbulent Flows ◽  
Numerical Study ◽  
Three Dimensional ◽  
Free Water ◽  
Lateral Wall ◽  
Lateral Spreading ◽  
Propagation Length ◽  
Vertical Slot ◽  
Surface Jets

The efficiency of a fishway is determined by the ability of immigrating fish to follow its attraction flow (i.e., its jet) to locate and enter the fishway entrance. The hydraulic characteristics of fishway entrance jets can be simplified using findings from widely investigated surface jets produced by shaped nozzles. However, the effect of the different boundary conditions of fishway entrance jets (characterized by vertical entrance slots) compared to nozzle jets must be considered. We investigate the downstream propagation of attraction jets from the vertical slot of a fishway entrance into a quiescent tailrace, considering the following boundary conditions not considered for nozzle jets: (1) slot geometry, (2) turbulence characteristics of the approach flow to the slot, and (3) presence of a lateral wall downstream of the slot. We quantify the effect of these boundary conditions using three-dimensional hydrodynamic-numeric flow simulations with DES and RANS turbulence models and a volume-of-fluid method (VoF) to simulate the free water surface. In addition, we compare jet propagation with existing analytical methods for describing jet propagations from nozzles. We show that a turbulent and inhomogeneous approach flow towards a vertical slot reduces the propagation length of the slot jet in the tailrace due to increased lateral spreading compared to that of a jet produced by a shaped nozzle. An additional lateral wall in the tailrace reduces lateral spreading and significantly increases the propagation length. For highly turbulent flows at fishway entrances, the RANS model tends to overestimate the jet propagation compared to the transient DES model.

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