Intensification of mixing of fuel with supersonic air flow when injection and electric discharge are combined

This paper presents the results of experimental investigations of DC discharge influence on mixing intensification of transvers injected gas jet into supersonic aiflow. The air was used as injected gas to prevent the influence of chemical reactions on measurements. The data obtained during discharge includes current and voltage acquisition, registration of pressure pulsations in the jet downstream of discharge operation accompanied by correlation and Fourier analysis allowed to conclude that discharge significantly increase the pressure pulsations in a wide frequency range of 1000 Hz to 50kHz. Increase of the oscillations near the jet boundary is assumed to be related to kinematic mixing intensification of the injected gas with the oncoming flow.

Numerical Analysis of Fairings for Bicycles

Aerodynamics is the study of moving air's properties and the interactions between moving air and solids. Rider gets slammed into air particles while riding that gets compressed once rider hit them and then become spaced out once they flow over the rider. The distinction in atmospheric pressure from your front to your back creates a retardant force. The force that's perpendicular to the oncoming flow direction is the lift force. It contrasts with the drag force. Aerodynamic shapes reduce this pressure drag and lift by minimizing that difference in pressure and allowing the air to flow more smoothly over your front, reducing the low-pressure wake behind the cyclist and reducing this drag, and increasing speed in this paper; fairings designed. NACA airfoil as a base, fairings are designed using CATIA.CFD analysis is carried out on the bicycle with a fairing to calculate drag and lift force. As the position of cyclists isn't modified and due to fairing, the air resistance reduces, which may increase the comfort level of cyclists. From this analysis, the economical fairing can be determined, facilitating additional drag and producing less lift.

Modelling of the flow in front of the jet obstacle at variation of oncoming flow parameters

The results of numerical simulation of the problem of interaction of supersonic flow with a jet obstacle under variation of input flow parameters are considered. The problem is solved in the system of Navier-Stokes equations. Laminar flows are considered. The qualitative flow pattern has been studied under the variation of incoming flow velocity and boundary layer thickness in the incoming flow. The calculations were performed using the OpenFOAM software package.

DARRIEUS TYPE WIND TURBINE WITH CONTROLLED BLADES

The results of studies on possibility of increasing efficiency in the use of wind energy and improving the dynamic characteristics of Darrieus wind turbine with straight blades are described. It is shown how the values of torque on the rotor shaft may be optimized by controlling the orientation of the turbine blades relative to the oncoming flow. Control of blades was provided with a cylindrical track of the special form in plan. The track form allowed to establish optimum angle of attack on each site of blade circular trajectory. It allowed to increase power coefficient Cp by 1.5 times and to reduce wind speed at which there is self-start of the wind turbine

Transcritical flow over obstacles and holes: forced Korteweg–de Vries framework

This paper extends a previous study of free-surface flow over two localised obstacles using the framework of the forced Korteweg–de Vries equation, to an analogous study of flow over two localised holes, or a combination of an obstacle and a hole. Importantly the terminology obstacle or hole can be reversed for a stratified fluid and refers more precisely to the relative polarity of the forcing and the solitary wave solution of the unforced Korteweg–de Vries equation. As in the previous study, our main concern is with the transcritical regime when the oncoming flow has a Froude number close to unity. In the transcritical regime at early times, undular bores are produced upstream and downstream of each forcing site. We then describe the interaction of these undular bores between the forcing sites, and the outcome at very large times.

Mapping the properties of the vortex-induced vibrations of flexible cylinders in uniform oncoming flow

Flexible structures placed within an oncoming flow exhibit far more complex vortex-induced dynamics than flexibly mounted rigid cylinders, because they involve the distributed interaction between the structural and wake dynamics along the entire span. Hence, mapping the well-understood properties of rigid cylinder vibrations to those of strings and beams has been elusive. We show here with a combination of experiments, conducted at Reynolds number, $Re$ from 250 to 2300, and computational fluid dynamics that such a mapping is possible for flexible structures in uniform flow undergoing combined cross-flow and in-line oscillations, but only when additional concepts are introduced to model the extended coupling of the flow and the structure. The in-line response consists of largely standing waves that define cells, each cell spanning the distance between adjacent nodes, over which stable vortical patterns form, whose features (‘2S’ versus ‘P$+$S’) depend strongly on the true reduced velocity, $V_{r}=U/f_{y}d$, where $U$ is the inflow velocity, $f_{y}$ is the cross-flow vibration frequency and $d$ is the cylinder diameter, and the phase angle between in-line and cross-flow response; while the cross-flow response may contain travelling waves, breaking the symmetry of the problem. The axial distribution of the highly variable effective added masses in the cross-flow and in-line directions, and the local phase angle between in-line and cross-flow motion determine the single frequency of cross-flow response, while the in-line response vibrates at twice the cross-flow frequency. The cross-flow and in-line lift coefficients in phase with velocity depend strongly on the true reduced velocity but also on the local phase angle between in-line and cross-flow motions. Modal shapes can be defined for in-line and cross-flow, based on the resemblance of the response to conventional modes, which can be in the ratio of either ‘$2n/n$’ or ‘$(2n-1)/n$’, where $n$ is the order of the cross-flow response mode. We use an underwater optical tracking system to reconstruct the sectional fluid forces in a flexible structure and show that, once the cross-flow and in-line motion features are known, employing strip theory and the hydrodynamic coefficients obtained from forced rigid cylinder experiments allows us to predict the distributed forces accurately.

Interaction of viscous free-surface flows with topography

The interaction of gravitationally driven, free-surface flows of viscous fluid with topographic features is investigated theoretically. The motion is studied in the regime where the depth of the flow is much smaller than the streamwise extent of the topography. A lubrication model of the motion is developed, integrated numerically and analysed asymptotically. For small mounds, it is shown that the flow surmounts the obstacles, but for larger mounds the flow is deflected around it and can form dry zones in its wake into which fluid does not flow, as well as forming deeper ponded regions upstream. Which of these phenomena prevails is shown to depend upon the amplitude of the mound height and the thickness of the oncoming flow relative to the streamwise length scale over which the topography varies. By using numerical and asymptotic results, we demonstrate that relatively wide mounds lead to the development of deep ponds of material upstream, which may lead to flow overtopping if the mound is not sufficiently high. These insights can be used to inform the design of barriers that defend built infrastructures from lava flows, and it is shown how this model can also provide an upper bound on the force exerted by the flow on them.