Three-Dimensional Calculation of a Hydrogen Jet Injection into a Supersonic Air Flow

1993 ◽  
pp. 402-412
Keyword(s):  
Air Flow ◽  
Three Dimensional ◽  
Jet Injection

Effects of Increasing Inlet Velocities and Side Port Air Injection on a Biomass Fluidizing Bed

2010 ◽  
Author(s):  
Mirka Deza ◽  
Francine Battaglia
Keyword(s):  
Complex Geometry ◽  
Air Flow ◽  
Three Dimensional ◽  
Air Injection ◽  
Single Side ◽  
X Ray Computed ◽  
Bed Material ◽  
Solid Distribution ◽  
Side Port ◽  
Three Dimensional Simulations

Fluidized beds are being used in practice to gasify biomass to create producer gas, a flammable gas that can be used for process heating. However, recent literature has identified the need to better understand and characterize biomass fluidization hydrodynamics, and computational fluid dynamics (CFD) is one approach in this effort. Previous work by the authors considered the validity of using two-dimensional versus three-dimensional simulations to model a cold-flow fluidizing biomass bed configured with a single side port air injection. The side port is introduced to inject air and promote mixing within the bed. Comparisons with experiments indicated that three-dimensional simulations were necessary to capture the fluidization behavior for the more complex geometry. This paper considers the effects of increasing fluidization air flow and side port air flow on the homogeneity of the bed material in a 10.2 cm diameter fluidized bed. Two air injection ports diametrically opposed to each other are also considered to determine their effects on fluidization hydrodynamics. Whenever possible, the simulations are compared to experimental data of time-averaged local gas holdup obtained using X-ray computed tomography. This study will show that increasing the fluidization and side port air flows contribute to a more homogeneous bed. Furthermore, the introduction of two side ports results in a more symmetric gas-solid distribution.

scholarly journals A three-dimensional theory of wind pumping

1991 ◽  
Vol 37 (125) ◽  
pp. 89-96 ◽  
Author(s):  
Garry K. C. Clarke ◽  
Edwin D. Waddington
Keyword(s):  
Heat Source ◽  
Surface Pressure ◽  
Air Flow ◽  
Pressure Fluctuations ◽  
Normal Component ◽  
Three Dimensional ◽  
Lower Atmosphere ◽  
Dimensional Theory ◽  
Theoretical Formulation ◽  
Near Surface

AbstractQuantitative understanding of the processes that couple the lower atmosphere to the upper surface of ice sheets is necessary for interpreting ice-core records. Of special interest are those processes that involve the exchange of energy or atmospheric constituents. One such process, wind pumping, entails both possibilities and provides a possible mechanism for converting atmospheric kinetic energy into a near-surface heat source within the firn layer. The essential idea is that temporal and spatial variations in surface air pressure, resulting from air motion, can diffuse into permeable firn by conventional Darcy flow. Viscous friction between moving air and the solid firn matrix leads to energy dissipation in the firn that is equivalent to a volumetric heat source.Initial theoretical work on wind pumping was aimed at explaining anomalous near-surface temperatures measured at sites on Agassiz Ice Cap, Arctic Canada. A conclusion of this preliminary work was that, under highly favourable conditions, anomalous warming of as much as 2°C was possible. Subsequent efforts to confirm wind-pumping predictions suggest that our initial estimates of the penetration depth for pressure fluctuations were optimistic. These observations point to a deficiency of the initial theoretical formulation — the surface-pressure forcing was assumed to vary temporally, but not spatially. Thus, within the firn there was only a surface-normal component of air flow. The purpose of the present contribution is to advance a three-dimensional theory of wind pumping in which air flow is driven by both spatial and temporal fluctuations in surface pressure. Conclusions of the three-dimensional analysis are that the penetration of pressure fluctuations, and hence the thickness of the zone of frictional interaction between air and permeable firn, is related to both the frequency of the pressure fluctuations and to the spatial coherence length of turbulence cells near the firn surface.

Assessment of digital image correlation vibrometry in the presence of thermal flow disturbance

2021 ◽  
Vol 263 (3) ◽  
pp. 3861-3870
Author(s):  
Kenji Homma ◽  
Paul R. Braunwart ◽  
Patrick L. Clavette
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Air Flow ◽  
Three Dimensional ◽  
Laser Doppler Vibrometer ◽  
Image Correlation ◽  
Stereo Pair ◽  
Structural Vibrations ◽  
Heated Air ◽  
Extraneous Noise

Digital Image Correlation (DIC) is an image-based method for measuring displacement and/or stain on the surface of a structure. When coupled with a stereo pair of highspeed cameras, DIC can also capture three-dimensional dynamic deformation of a structure under vibratory loading. However, high frequency and small amplitude displacement typically associated with structural vibrations mean that extra care is required during measurement and data processing. It becomes more challenging when thermal disturbances are present in the optical path, for example from a heated air flow, which introduces extraneous noise due to disturbances in the refractive index. In the present study, a simple composite plate was vibrated under a shaker excitation and stereo DIC measurements were performed. The obtained vibratory displacement results were compared against accelerometers and a laser Doppler vibrometer. Heated air flow was introduced in front of the plate to observe the effects of thermal disturbances on the DIC measurements. Although the contributions from the thermal disturbances were clearly visible in the DIC displacement data, it was shown that the vibratory deflections of the structure could still be extracted by post processing of the DIC data.

THREE-DIMENSIONAL SIMULATIONS OF DROP DEFORMATION AND BREAKUP IN AIR FLOW AND COMPARISONS WITH EXPERIMENTAL OBSERVATIONS

2018 ◽  
Vol 28 (7) ◽  
pp. 621-641 ◽  
Author(s):  
Chao Liang ◽  
Kathleen A. Feigl ◽  
Franz X. Tanner ◽  
William R. Case ◽  
Erich J. Windhab
Keyword(s):  
Air Flow ◽  
Three Dimensional ◽  
Drop Deformation ◽  
Three Dimensional Simulations

Three-Dimensional/One-Dimensional Combined Simulation of Deep Surge Loop in a Turbocharger Compressor With Vaned Diffuser

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Ghislaine Ngo Boum ◽  
Rodolfo Bontempo ◽  
Isabelle Trébinjac
Keyword(s):  
System Modeling ◽  
Air Flow ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Vaned Diffuser ◽  
One Dimensional ◽  
Compressor Surge ◽  
Important Challenge ◽  
Unsteady Rans ◽  
Combined Simulation

High accuracy simulation of compressor surge origin and growth is an important challenge for designers of systems using compressors likely to develop that severe instability. Indeed, understanding its driving phenomena, which can be system dependent, is necessary to build an adequate strategy to avoid or control surge emergence. Computational fluid dynamics (CFD) simulations, commonly used to explore flow in the compressor, need then to be extended beyond the compressor as surge is a system scale instability. To get an insight on the path to surge and through surge cycles, a reliable alternative to full three-dimensional (3D) system modeling is used for a turbocharger compressor inserted in an experimental test rig. The air flow in the whole circuit, is modeled with a one-dimensional (1D) Navier Stokes approach which is coupled with a 3D unsteady RANS modeling of the 360 deg air flow in the centrifugal compressor including the volute. Starting from an initial stable flow solution in the system, the back-pressure valve is progressively closed to reduce the massflow and trigger the instability. An entire deep surge loop is simulated and compared with good agreement with the experimental data. The existence of a system-induced convective wave is revealed, and its major role on surge inception at diffuser inlet demonstrated.

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