Vortex Flow Control Research Articles

Influence of different turbulence models on tip vortex prediction

Abstract Tip vortex cavitation usually occurs in marine propellers and axial-flow turbines, the cavitation in the tip vortex could potentially result in blade erosion, at the same time, it will cause the pump vibration and noise emission. The tip vortex mainly occurs in rotating machinery with complex three-dimensional flow, but the prediction of the hydrofoil tip vortex can provide a basis for the study of the blade tip vortex in rotating machinery by simplifying the blade model. Hence, in this paper, we use the commercial software CFX to investigate the impact of distinct turbulence models on the configuration of tip vortex distribution in the NACA 16-020 hydrofoil, including SST (Shear Stress Transport), DES (Detached Eddy Simulation), LES (Large Eddy Simulation) turbulence models which are widely used in the field of rotating machinery. At the same time, the axial and radial velocity distributions at different locations downstream of the tip of the hydrofoil are compared to analyse the effects on the velocity distribution near the vortex core line stemming from various turbulence models. By comparing with the experimental data, the most accurate turbulence model for tip vortex prediction is obtained, which will provide guidance for the next step tip vortex prediction and the control of tip vortex flow.

Comparison of argon injection and other methods of electrovortex flow control in metallurgical furnaces

The article considers the problem of modeling the metal melting in a direct current arc furnace with the bottom electrode. A mathematical model and a technique for conducting coupled modeling of magnetohydro- and thermodynamic flows in such a furnace are presented taking into account electromagnetic forces and convection. Using the developed strategy, simulations were performed and the effectiveness of some approaches to the vortex flow control was evaluated. As a result, it was shown that changing the location, shape, and temperature of the bottom electrode as well as the bottom position can significantly reduce fettle wearing near the electrode, while argon injection does not decrease shear stress and does a negative influence on the fettle.

The evolution of wingtip vortex wandering: a stability analysis based on stereo-PIV experiment

Instability, as a potential mechanism for vortex flow control, is manifested typically in the phenomenon of wingtip vortex wandering. In this paper, the evolution of wingtip vortex generated by a NACA0015 rectangular wing within six chord lengths of its wake at Rec= 2.1 × 105–3.5 × 105 and AoA = 4°–10° is investigated by stereo particle image velocimetry experiment. The streamwise evolution of vortex wandering is clearly captured, which demonstrates strong anisotropy. The amplitude of vortex wandering increases under all conditions, which exhibits greater growth rates in the condition of larger AoA. To account for such phenomenon, spatial linear stability analysis is performed on the base flow obtained by SPIV experiment to investigate quantitatively the amplification of small disturbance and disturbance modes at the experiment conditions. It is discovered that the wingtip vortex in the experiment is marginally stable under all conditions. Furthermore, the spatial growth rates of instability by AoA correspond well with that of wandering amplitude, indicating that the quick enlargement of the amplitude of wandering at larger AoA condition is caused by larger spatial growth rate of disturbance. In addition, the least-stable disturbance mode by LSA reveals a non-zero directed velocity perturbation in the vortex core, which rotates periodically. Such perturbation developing in both time and space, which is stirred by vortex instability, leads to the behavior of wingtip vortex wandering.

Dimensioning of vortex storm overflows.

Vortex storm overflow is an interesting and useful technical solution, especially important in storm and combined sewage systems. However, there are no methods of this device dimensioning, which would be mathematically simple and properly precise physically. Such a method has been proposed in this paper, on the basis of investigations performed for the vortex separators and vortex flow controls. The essence of this method relies on the kinematic model of the velocity field and energy balance of the inflowing stream and dissipation. The procedure enables specialists to calculate the rise of the liquid free surface caused by the inlet stream energy and the hydraulic resistance of the bottom outlet. These mathematical relations are completed by two formulae: for the bottom 'morning glory' sink and for the upper overflow. The model has been positively verified during the laboratory measurements, so can be used during the technical dimensioning of the vortex storm overflows.

Enhanced Maneuverability of a Delta-Canard Combat Aircraft by Vortex Flow Control

Delta-canard shapes allow for maneuverable, supersonic combat aircraft. A configuration of medium aspect ratio was investigated to extend its maneuverability to very high angle of attack. Here, leading-edge vortex flows with intense interaction and breakdown effects dominate the flow. To appreciably enhance the maneuverability beyond limits, aerodynamic means had to be found. In-depth understanding of the interactions of the vortex systems was necessary to improve the aircraft capabilities. Unsteady Reynolds-averaged Navier-Stokes simulations simulations were performed via the unstructured DLR-Tau code. The aircraft was modeled without compromising geometrical details. It was found that asymmetric vortex breakdown features and unfavorable interactions at sideslips are the cause of the limited maneuverability. Means were deduced to control the vortex systems to mitigate or even avoid previous limits. This was done via a combination of theoretical thinking and computational fluid dynamics flow simulations. Aerodynamic means to control the lateral stability were investigated. Wind-tunnel tests secured this process. Small but effective fuselage strakes and leading-edge root extensions between the canard and the wing enhanced the lateral stability considerably. Much higher angle of attack can be reached for increased maneuverability. The design concept was confirmed through intense wind-tunnel campaigns and successfully flown in a test program covering the envelope.

Free-surface elevation in open vortex flow controls

Among many practical applications in hydraulic engineering, rotational separators of a suspension and vortex flow controls may serve as especially interesting examples. This form of motion, despite some evident regularity, is a complex phenomenon so to describe it one should make use of CFD tools or pursue an experimental approach to the subject. Both of these possibilities are not very convenient, so any rational method that provides a possibility for calculating the velocity field and pressure distribution is welcome. For the considered class of technical objects, the family of kinematic models is to the purpose. The velocity field is described in this case by some algebraic relations, assumed arbitrarily on the basis of a qualitative evaluation of this field and the model constant is calculated from a delivered and dissipated energy in the energy balance. This method was effectively used in the description of rotational separators and pressure flow controls operation. This paper presents an application of such an approach to open flow regulators.

Asymmetric Flow Control on a Delta Wing with Dielectric Barrier Discharge Actuators

This paper presents an experimental investigation of the effect of the dielectric barrier discharge plasma actuators on the leading-edge vortex flow control over a delta wing with a 75 deg swept angle. The Reynolds number based on the delta wing chord is 50,000. The smoke flow visualization and particle image velocimetry experiments in the wind tunnel indicate that the asymmetric control caused by the dielectric barrier discharge plasma actuator can significantly affect the global flow structure over the delta wing: the leading-edge vortex breakdown position on the same side of the actuator is advanced, whereas vortex breakdown on the other side is delayed. This phenomenon is observed for the first time and is only observed in the current full-span delta wing experiment, significantly different from the result of the semispan experiment. The force measurement result shows that the asymmetric control has a limited contribution to lift generation but can induce a relatively large roll moment.

Model of Pressure Distribution in Vortex Flow Controls

Abstract Vortex valves belong to the category of hydrodynamic flow controls. They are important and theoretically interesting devices, so complex from hydraulic point of view, that probably for this reason none rational concept of their operation has been proposed so far. In consequence, functioning of vortex valves is described by CFD-methods (computer-aided simulation of technical objects) or by means of simple empirical relations (using discharge coefficient or hydraulic loss coefficient). Such rational model of the considered device is proposed in the paper. It has a simple algebraic form, but is well grounded physically. The basic quantitative relationship, which describes the valve operation, i.e. dependence between the flow discharge and the circumferential pressure head, caused by the rotation, has been verified empirically. Conformity between calculated and measured parameters of the device allows for acceptation of the proposed concept.

Modelling of vortex flow controls at high drainage flow rates

A number of vortex flow control (VFC) devices for urban drainage systems are investigated computationally at high flow rates, for which a confined vortex dominates the flow regime. A range of turbulence models, including both eddy viscosity and Reynolds stress closures, are compared with in-house experimental measurements of head loss and internal pressure measurements. Single-phase and multi-phase (free surface) calculations are also compared. Very good agreement with the experimental data was obtained when the swirl parameter of the device was below 3·14 for predictions made using the Reynolds stress closure formulations. For devices with swirl parameters above this value, the computational methodology was found to under-predict the head loss of the device. This was attributed to poor calibration of the turbulence model for swirling flow scenarios in which the pressure gradient and diffusive (turbulent) forces in the flow are comparable.

Developing a Decision Support Tool for the Positioning and Sizing of Vortex Flow Controls in Existing Sewer Systems

This paper describes the development of a decision support tool for the positioning and sizing of vortex flow controls in existing sewer systems. The tool aims to prioritise the placement of vortex flow controls primarily within subcatchments with the greatest flood consequence rating and maximise the use of unused inpipe volumes during critical rainfall events. The decision support tool is intended for use in catchments where opportunities to implement SuDS and rainwater harvesting to defend against flooding are limited. The decision support tool is envisaged to identify potential strategies which could enhance flood resistance of sewer systems in a cost effective manner.

Computational fluid dynamics of vortex flow controls at low flow rates

A vortex flow control with differing outlet shapes is investigated computationally at low flow rates. The volume of fluid method was utilised to track the moving free surface. In order to achieve a smooth free surface, interface compression coupled with the inter-gamma compressive scheme was used. The turbulent evolution of the two-phase flow was modelled by solving the Reynolds-averaged Navier–Stokes equations with the k–ε model for turbulent quantities. Validation of the results was carried out by analysing the total head and discharge coefficient for the three outlet shapes at various flow rates and comparing these results with experimental data. Very good agreement with the experimental data was obtained.

The Hydraulic Stability of Heating Network with Remote Measurement and Control System

In order to eliminate hydraulic imbalance phenomenon of the heating network, this article briefly introduces the operation principle of the system. The remote control system uses computer information and communication technology to monitor the network flow, through the pressure curve to estimate the hydraulic condition. According to the analysis of pipe resistance properties and the hydraulic balance calculation, the system will change the valve opening intelligently, to make the heating network running in a hydraulic balance condition. The vortex flow meter and flow control valve can be used to adjust the water flow of primary and secondary network, such measure will ensure the hydraulic stability of heating system, save the thermal energy consumption.

Plasma control of vortex flow on a delta wing at high angles of attack

The flow over a delta wing at high angles of attack is characterized by the presence of two large-scale primary vortices on the leeward side of the wing. These vortices contribute substantially to lift production at high angles of attack. Therefore, vortex breakdown, which can be induced by unfavorable pressure gradients or free-stream disturbances, can lead to an abrupt decrease in lift and to the emergence of a roll moment. Thus, the possibility of vortex flow control can be very useful. The problem of vortex flow control is investigated experimentally under subsonic flow parameters in the range of wing chord-based Reynolds number (0.14, 0.25) × 106. A dielectric barrier discharge (DBD) is used as an active control actuator. The data obtained by means of oil flow and smoke flow visualization, surface pressure measurements, and using a particle image velocimetry technique show that the DBD can provoke early vortex bursting. Under certain conditions (discharge excitation mode and frequency), flow excitation by the discharge actuator is found to result in vortex stabilization.

On the pressure drop and the velocity distribution in the cylindrical vortex chamber with two inlet pipes for the control of vortex flow

Vortex flow is applied to a cyclone dust collector, a vortex combustion chamber, and a vortex diode for vortex control. In order to apply the vortex flow to the industries, it is necessary to keep the stable flow condition and to estimate the response time of the transient flow process and also the intensity of the vortex flow. For control vortex flow, two types of vortex chamber with two inlet pipes were designed. One of them is to promote the vortex flow named as Co-Rotating Flow System and another one is to hinder the vortex flow named as Counter-Rotating Flow System. The pressure drops and the velocity distributions were measured for these vortex chambers. The estimation of the tangential velocity by the application of the angular momentum flux is compared with the measured velocity by a cylindrical Pitot-tube. The characteristics of the total pressure drop could be explained by introducing the circulation.

G105 偏心二重円筒間に発生するTaylor渦流れの非定常挙動に関する数値解析(GS-1 種々な流動現象,一般セッション)

G105 偏心二重円筒間に発生するTaylor渦流れの非定常挙動に関する数値解析(GS-1 種々な流動現象,一般セッション)

渦制御を目的とした円筒形渦室の圧力損失と気流の周分速度分布(流体工学II-3)

渦制御を目的とした円筒形渦室の圧力損失と気流の周分速度分布(流体工学II-3)

Microblowing for High-Angle-of-Attack Vortex Flow Control on a Fighter Aircraft

Effectiveness of the microblowing technique for controlling forebody vortex asymmetry at high angles of attack has been investigated in low-speed wind-tunnel experiments with the F-15E fighter aircraft configuration. One blowing-port installation, based on previous experiments with generic forebody shapes, was evaluated. At very high angles of attack (a > 50 deg), microblowing was effective in generating and controlling yawing moment levels comparable to those demonstrated by high-pressure jet nozzle blowing, while requiring only 1/100 as much mass flow, demonstrating the leveraging available through controlling the vortex flowfield at the point of instability. The microblowing port configuration employed was unable to generate usable yawing moments at moderate angles of attack (α≤35 deg). Control-port optimization promises to improve microblowing effectiveness in the intermediate α range

Experimental study of vortex flow control on double-delta wings using fillets

An experimental investigation of vortex flow control through small geometry modifications (fillets) at the strake/wing junction of a cropped, double-delta whig model with sharp leading edges was conducted in a water tunnel at a model Reynolds number of 1.875 X 10. The fillets increased the whig area of the baseline model by 1%. The main focus of this study was to evaluate the effects of fillets on vortex core trajectories, interactions, and breakdown (bursting) on the leeward surface at high angles of attack (AOAs), using the dye-injection technique. Comparison of test results for different fillet shapes indicates delay hi both vortex interaction and breakdown at high AOAs, particularly for the diamond-fillet shape. The vortex trajectory data for the diamond-fillet shape clearly imply lift augmentation, thus supporting the concept of flow control using fillets. The vortex breakdown data indicate lift augmentation for both the static and dynamic cases.

F-15 forebody vortex flow control using jet nozzle blowing

A low-speed wind-tunnel test was conducted to determine the lateral-directional control effectiveness of a forebody jet nozzle blowing on a 10% scale F-15E model. This investigation of pneumatic forebody vortex flow control was the first of its kind performed on an F-15 configuration. The test acquired sixcomponent force balance data in the NASA Langley 30- by 60-Foot Tunnel at a freestream dynamic pressure of 8 psf at an equivalent Reynolds number per foot of approximately 5.08 X 10 5. Asymmetric forebody jet blowing was effective in generating yawing moments through an angle of attack (AOA) range that extends beyond the limit of rudder control power. The optimum nozzle configurations were pointed outward, and yawing moments generated within the maneuver range of AOA (a < 40 deg) increased with increases in both blowing rate and AOA. Above 10-deg AOA, blowing rates of C M = 0.010 and greater resulted in yawing moments that approached or exceeded that developed by full rudder deflection.

Nonlinear vortex flow control for high-angle-of-attack maneuvering

The research covered in this paper explores the feasibility of expanding the flight envelope of a modified VISTA F-16 to higher angles-of-attack through forebody vortex flow control. The forebody vortex system is controlled with a pneumatic (blowing) forebody control system. The vortex blowing system is driven by nonlinear control laws that are derived using Variable Structure Control and describing function techniques. Nominal stability, robust stability, limit cycle, and nonlinear performance analyses are performed to examine control system performance. Results reveal that additional yaw control power from the blowing control system provides significant improvement in high-a performance.