Directed Particle-Laden Micro-Jet for Dental Caries Evacuation (Keynote Paper)

2003 ◽  
Author(s):  
Michael Amitay ◽  
Shayne Kondor ◽  
Scott Herdic ◽  
Steven L. Anderson
Keyword(s):  
Dental Caries ◽  
Flow Field ◽  
Active Control ◽  
High Speed ◽  
Cross Flow ◽  
Jet Flow ◽  
Spreading Rate ◽  
Exit Plane ◽  
Keynote Paper ◽  
The Cross

Active and passive approaches to control the velocity and concentration of a high speed round particle-laden jet are investigated experimentally using a stereo PIV system. Active control of the flow field and the particles’ velocity and concentration fields, via the addition of swirl to the carrier jet, has shown to have a significant effect in altering both phases. Control is also affected by placing passive pins at the jet exit plane, which results in alteration of the velocity in planes across and normal to the pins. Furthermore, the mixing is increased and the spreading rate is modified. Depending on the number of pins used and their azimuthal location, their interaction with the carrier jet flow lead to the modification of the cross-flow shape of the jet and the direction of the flow.

Influence of Mainstream Cross Flow on Film Cooling Performance and Jet Flow Field

2017 ◽  
Author(s):  
Yifei Li ◽  
Yang Zhang ◽  
Xinrong Su ◽  
Xin Yuan
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Gas Turbines ◽  
Cross Flow ◽  
Jet Flow ◽  
Secondary Flows ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Significant Difference ◽  
The Cross

The influence of the cross flow in mainstream on film cooling performance and jet flow field is investigated experimentally and numerically. To show the effect of cross flow in mainstream without the influence of the other secondary flows, a curved test section is constructed to generate a cross flow, simulating the curved turbine passage. Both the straight and the curved passage are used to show the differences of cooling performance for shaped holes with and without the cross flow, with blowing ratio varying from M = 0.5 to M = 2.5. Pressure sensitive paint is used to measure the adiabatic cooling effectiveness, and the ink trace measurement is conducted to present the friction lines on the endwall platform. Numerical simulations are performed to show the flow field. The cross flow is accelerated in a curved passage and migrates the fluid near the endwall platform. Due to the cross flow in the mainstream, the deflection angle changes a lot along the normal direction to the endwall, and dominates the spatial distribution of coolant. Although the cooling trace follows the trend of wall surface streamlines, the migration of coolant is slower than the deviation of the friction line, and the difference increases with increasing blowing ratios. The cross flow enhances the lateral dispersion, decreasing the peak value of cooling effectiveness but increasing the laterally averaged cooling effectiveness. Higher blowing ratios lead to a higher intensity of a counter-rotating vortex pair that limits lateral dispersion near the outlet of cooling hole. But the effect of cross flow dominates the flow pattern downstream. The cooling performance has a significant difference with the influence of the cross flow. This study is essential to understand the interaction of the cross flow and the film cooling in gas turbines.

Turbulence-Induced Vibration of Tube Bundle in Cross and Parallel Jet Mixed Flow

1989 ◽  
Vol 111 (4) ◽  
pp. 352-360 ◽  
Author(s):  
K. Kawamura ◽  
A. Yasuo
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Flow Field ◽  
Tube Bundle ◽  
Cross Flow ◽  
Jet Flow ◽  
Fretting Wear ◽  
Baffle Plate ◽  
Mixed Flow ◽  
The Cross

In the multi-tube type of heat exchanger, baffle plates are located at appropriate intervals to support the heat transfer tubes. Depending on the baffle plate type employed, the flow field in the tube bundle will consist of a mixture of the cross flow (the fluid flows at right angles to the tube bundle along the baffle plate surfaces) and the parallel jet flow (the fluid streams through channels such as the flow holes of the baffle plates in the form of jets and flows in parallel with the tube bundle). Vibrations induced by the flow can cause fretting wear and fatigue of the heat transfer tubes. Therefore, it it essential to establish a method of evaluating heat transfer tube vibrations induced by the mixed flow for the purpose of evaluating the integrity of heat exchanger tubes. In this paper, three different flows, that is, cross, parallel jet and mixed flows, were simulated in order to clarify the relationships between the flow conditions and vibration of the tube bundle, and to study a method for evaluating tube bundle vibrations induced by turbulence in the mixed flow field by using the vibration characteristics in the cross flow field and the parallel jet flow field.

scholarly journals Cross-Flow Tidal Turbines with Highly Flexible Blades—Experimental Flow Field Investigations at Strong Fluid–Structure Interactions

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 797
Author(s):  
Stefan Hoerner ◽  
Iring Kösters ◽  
Laure Vignal ◽  
Olivier Cleynen ◽  
Shokoofeh Abbaszadeh ◽  
...  
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Cross Flow ◽  
Speed Ratio ◽  
Fluid Structure Interactions ◽  
Dimensional Parameter ◽  
Fluid Structure ◽  
Passive Flow Control ◽  
Tidal Turbines ◽  
Tidal Turbine

Oscillating hydrofoils were installed in a water tunnel as a surrogate model for a hydrokinetic cross-flow tidal turbine, enabling the study of the effect of flexible blades on the performance of those devices with high ecological potential. The study focuses on a single tip-speed ratio (equal to 2), the key non-dimensional parameter describing the operating point, and solidity (equal to 1.5), quantifying the robustness of the turbine shape. Both parameters are standard values for cross-flow tidal turbines. Those lead to highly dynamic characteristics in the flow field dominated by dynamic stall. The flow field is investigated at the blade level using high-speed particle image velocimetry measurements. Strong fluid–structure interactions lead to significant structural deformations and highly modified flow fields. The flexibility of the blades is shown to significantly reduce the duration of the periodic stall regime; this observation is achieved through systematic comparison of the flow field, with a quantitative evaluation of the degree of chaotic changes in the wake. In this manner, the study provides insights into the mechanisms of the passive flow control achieved through blade flexibility in cross-flow turbines.

Experimental and numerical analyses of gas–solid-multiphase jet in cross-flow

2012 ◽  
Vol 227 (1) ◽  
pp. 61-79 ◽  
Author(s):  
Yao Fu ◽  
Tong Wang ◽  
Chuangang Gu
Keyword(s):  
Flow Field ◽  
Transient Flow ◽  
Cross Flow ◽  
Jet Flow ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Calculation Methods ◽  
Mean Flow ◽  
Eddy Simulation ◽  
Reynolds Averaged Navier Stokes

In this article, jet influence on a gas–solid-multiphase channel flow was experimentally and numerically studied. The jet flow was found to have a diameter-selective controlling effect on the particles’ distribution. Jet flow formed a gas barrier in the channel for particles. While tiny particles could travel around and large particles could travel through, only particles on the 10 -µm scale were obviously affected. Three different calculation methods, Reynolds averaged Navier–Stokes, unsteady Reynolds averaged Navier–Stokes, and detached eddy simulation, were used to simulate this multiphase flow. By comparing the calculation results to the experimental results, it is found that all the three calculation methods could capture the basic phenomenon in the mean flow field. Nevertheless, there exist great differences in the transient flow field and particle distribution.

scholarly journals Effect of Jet Inclination Angle and Hole Exit Shape on Vortical Flow Structures in Low-Reynolds Number Jet in Cross-Flow

2012 ◽  
Vol 2012 ◽  
pp. 1-7
Author(s):  
Yufeng Yao ◽  
Mohamad Maidi ◽  
Jun Yao
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Inclination Angle ◽  
Qualitative Agreement ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Vortical Flow ◽  
Flow Structures ◽  
Good Qualitative Agreement ◽  
The Cross

Numerical studies have been performed to visualize vortical flow structures emerged from jet cross-flow interactions. A single square jet issuing perpendicularly into a cross-flow was simulated first, followed by two additional scenarios, that is, inclined square jet at angles of 30° and 60° and round and elliptic jets at an angle of 90°, respectively. The simulation considers a jet to cross-flow velocity ratio of 2.5 and a Reynolds number of 225, based on the free-stream flow quantities and the jet exit width in case of square jet or minor axis length in case of elliptic jet. For the single square jet, the vortical flow structures simulated are in good qualitative agreement with the findings by other researchers. Further analysis reveals that the jet penetrates deeper into the cross-flow field for the normal jet, and the decrease of the jet inclination angle weakens the cross-flow entrainment in the near-wake region. For both noncircular and circular jet hole shapes, the flow field in the vicinity of the jet exit has been dominated by large-scale dynamic flow structures and it was found that the elliptic jet hole geometry has maximum “lifted-off” effect among three hole configurations studied. This finding is also in good qualitative agreement with existing experimental observations.

Heat Transfer and Fluid Flow of a Single Jet Impingement in Cross-Flow Modified by a Vortex Generator Pair

2016 ◽  
Author(s):  
Chenglong Wang ◽  
Lei Luo ◽  
Lei Wang ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Gas Turbines ◽  
Cross Flow ◽  
Vortex Generator ◽  
Jet Impingement ◽  
Transfer Coefficients ◽  
Stagnation Region ◽  
Target Wall ◽  
The Cross

Jet impingement cooling is widely used in modern gas turbines. In the present study, both heat transfer and flow field measurements of jet impingement in cross-flow are carried out with and without a vortex generator pair (VGP). The jet and cross-flow Reynolds numbers are fixed at 15,000 and 48,000, respectively. The local heat transfer coefficients are obtained by a liquid crystal thermography (LCT) technique. Results show that the jet impingement heat transfer on the target wall is remarkably enhanced by the VGP as compared to the baseline case. The stagnation region moves upstream with improved heat transfer when the VGP is present. The flow field is measured by particle image velocimetry (PIV). The cross-flow is shown to deflect the impinging jet but the VGP reduces the streamwise momentum of the cross-flow and drives the crossflow away from the issuing jet. This leads to stronger jet impingement and thus heat transfer enhancement on the target wall.

Experimental and Numerical Investigation of the Flow Field at Radial Holes in High-Speed Rotating Shafts

2012 ◽  
Author(s):  
Jan Sousek ◽  
Daniel Riedmüller ◽  
Michael Pfitzner
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Discharge Coefficient ◽  
Cross Flow ◽  
Test Rig ◽  
Flow Phenomena ◽  
Rotating Shafts ◽  
Secondary Air ◽  
The One ◽  
Discharge Behaviour

Rotating and stationary orifices are used within the secondary air system to transport sealing/ cooling air to its consumers. This paper reports on measurements of the discharge coefficient of rotating radial holes as their aerodynamical behaviour is different from the one of axial or stationary holes due to the presence of centrifugal and Coriolis forces. A test rig containing two independently rotating shafts was designed to investigate the flow phenomena and the discharge behaviour of these orifices. The required air mass flow is delivered by a screw compressor and can be regulated independently to supply the inner and outer annular passages of the test rig. It allows measurements of the discharge coefficient with cross flow and co- and counter-rotating shafts with centrifugal and centripetal flow through the rotating holes. On the outer shaft, absolute and differential pressures and temperatures in the rotating frame of reference are measured via a telemetry system. Measurements of the discharge coefficient for sharp-edged and rounded shaft inserts at a variety of different flow conditions and with swirl added to the air upstream of the orifice are presented. Furthermore experiments were conducted to quantify the influence of the inner shaft (non-rotating and rotating) on the discharge behaviour of orifices in the outer shaft. To complement the data acquired from the experiments and to get a better understanding of the flow field near the rotating holes also numerical flow simulations were performed.

Simulation of Flow Induced Vibrations of Tube Bundle in Cross Flow

2001 ◽  
Vol 17 (3) ◽  
pp. 139-147
Author(s):  
Tsun-Kuo Lin ◽  
Ming-Huei Yu
Keyword(s):  
Flow Field ◽  
Natural Frequency ◽  
Stokes Equations ◽  
Tube Bundle ◽  
Cross Flow ◽  
Calculated Data ◽  
Major Axis ◽  
Damping Factor ◽  
Inlet Velocity ◽  
The Cross

ABSTRACTThe flow-induced vibration of tubes in a rotated triangular array subject to cross flow is simulated numerically. In the study, the flow field around the tube bundle is computed by solving the continuity and Navier-Stokes equations with assumption of constant fluid properties, and the kε-model for turbulent Reynolds stress. With the flow field known, the fluid forces on the tube surfaces can be calculated, and then the displacement of each tube due to the fluid force can be evaluated. Iteration is needed to obtain the dynamic response of the tube structure in the fluid flow. The parameters in the study are inlet velocity of the cross flow and properties of the tube bundle including natural frequency, damping factor, and mass. Based on the tube response, the critical flow conditions of tube vibration are determined for varying mass damping. Once tube vibrations occur, it is shown that the vibrations of the tubes in the second and fourth tube rows are significant as compared to other tubes. The orbits of the tube vibration look like an ellipse with major axis in the cross-stream direction, implying large lift force on the tubes. The dominant frequency in the spectrum of lift coefficients of the tubes is the same as the natural frequency, and the corresponding amplitude is increased with increasing the inlet velocity. The calculated data predicted for the critical reduced velocity agrees well with the data by Kassera and Strohmeier [17].

scholarly journals The interaction between a spatially oscillating jet emitted by a fluidic oscillator and a cross-flow

2019 ◽  
Vol 863 ◽  
pp. 215-241 ◽  
Author(s):  
Florian Ostermann ◽  
Rene Woszidlo ◽  
C. Navid Nayeri ◽  
C. Oliver Paschereit
Keyword(s):  
Flow Field ◽  
Strouhal Number ◽  
Cross Flow ◽  
Stereoscopic Particle Image Velocimetry ◽  
Time Dependent ◽  
Streamwise Vortices ◽  
Fluidic Oscillator ◽  
Jet Trajectory ◽  
Oscillating Jet ◽  
The Cross

This experimental study investigates the fundamental flow field of a spatially oscillating jet emitted by a fluidic oscillator into an attached cross-flow. Dominant flow structures, such as the jet trajectory and dynamics of streamwise vortices, are discussed in detail with the aim of understanding the interaction between the spatially oscillating jet and the cross-flow. The oscillating jet is ejected perpendicular to the cross-flow. A moveable stereoscopic particle image velocimetry (PIV) system is employed for the plane-by-plane acquisition of the flow field. The three-dimensional, time-resolved flow field is obtained by phase averaging the PIV results based on a pressure signal from inside the fluidic oscillator. The influence of velocity ratio and Strouhal number is assessed. Compared to a common steady wall-normal jet, the spatially oscillating jet penetrates to a lesser extent into the cross-flow’s wall-normal direction in favour of a considerable spanwise penetration. The flow field is dominated by streamwise-oriented vortices, which are convected downstream at the speed of the cross-flow. The vortex dynamics exhibits a strong dependence on the Strouhal number. For small Strouhal numbers, the spatially oscillating jet acts similar to a vortex-generating jet with a time-dependent deflection angle. Accordingly, it forms time-dependent streamwise vortices. For higher Strouhal numbers, the cross-flow is not able to follow the motion of the jet, which results in a quasi-steady wake that forms downstream of the jet. The results suggest that the flow field approaches a quasi-steady behaviour when further increasing the Strouhal number.

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