The analyzed wind field at 850 mb during the summer monsoon experiment (MONEX) is subjected to a time series analysis confirm existence of peak in range 30–50 days. Having established that, this study presents mapping motion for scale. In short paper we illustrate steady meridional propagation train troughs and ridges that seem form near equator dissipate Himalayas. scale mode around 300 km, its speed ∼0.75° latitude per day. amplitude 3–6 m s−1. salient contributions here are demonstration...

Laboratory experiments were performed on a geometrically scaled vertical-axis wind turbine model over an unprecedented range of Reynolds numbers, including and exceeding those the full-scale turbine. The study was in high-pressure environment Princeton High number Test Facility (HRTF). Utilizing highly compressed air as working fluid enabled extremely high numbers while still maintaining dynamic similarity by matching tip speed ratio (defined velocity to free stream,...

Abstract A formal relationship between the skewness and correlation coefficient of large small scales, termed amplitude modulation coefficient, is established for a general statistically stationary signal analysed in context turbulent velocity signal. Both quantities are seen to be measures phase triadically consistent interactions scales turbulence. The naturally existing relationships boundary layer then manipulated by exciting synthetic large-scale motion flow using spatially impulsive...

Abstract The variety of configurations for vertical-axis wind turbines (VAWTs) make the development universal scaling relationships even basic performance parameters difficult. Rotor geometry changes can be characterized using concept solidity, defined as ratio solid rotor area to swept area. However, few studies have explored effect this parameter at full-scale conditions due challenge matching both non-dimensional rotational rate (or tip speed ratio) and scale Reynolds number) in...

Abstract. We introduce an improved formulation of the double-multiple streamtube (DMST) model for prediction flow quantities vertical axis wind turbines (VAWT). The improvement new lies in that it renders DMST valid any induction factor, i.e., combination rotor solidity and tip speed ratio. This is done by replacing Rankine–Froude momentum theory DMST, which invalid moderate high factors, with a recently proposed, provides sensible results factor. predictions two formulations are compared...

Recent experimental studies reveal that the near-wake region of a circular cylinder at hypersonic Mach numbers exhibits self-sustained flow oscillations. The oscillation frequency was found to have universal behaviour. These oscillations are fundamentally different nature in comparison with caused due vortex shedding, which commonly observed wakes low-subsonic numbers. observations suggest an aeroacoustic feedback loop be driving mechanism high An analytical model successfully predicts...

Clouds are the largest source of uncertainty in climate science, and remain a weak link modeling tropical circulation. A major challenge is to establish connections between particulate microphysics macroscale turbulent dynamics cumulus clouds. Here we address issue from latter standpoint. First show how create bench-scale flows that reproduce variety cumulus-cloud forms (including two genera three species), track complete cloud life cycles--e.g., "cauliflower" congestus dissipating fractus....

The use of dynamic roughness or small, oscillating, wall elements to manipulate the structure turbulent boundary layers is reviewed with a view imposing true active control techniques. Linear and nonlinear responses simple oscillations are detailed, such that modifications overall turbulence interactions between scales can be inferred. Although work considered here uses mechanical actuation, approach sufficiently general implemented by range techniques, including engineered...

Coherent small-amplitude unsteadiness of the shock wave and separation region over a canonical double cone flow, termed in literature as oscillation-type unsteadiness, is experimentally studied at Mach 6. The model defined by three non-dimensional geometric parameters: fore- aft-cone angles ( $\theta _1$ _2$ ), ratio conical slant lengths $\varLambda$ ). Previous studies oscillations have been qualitative nature, mostly restricted to special case with fixed _1 = 0^\circ$ _2 90^\circ$...

Vertical Axis Wind Turbines have yet to see wide-spread use as a means of harvesting the kinetic energy wind. This may be due in part difficulty modeling relatively complex flow field and hence performance these units. Additionally, similar Horizontal Turbines, VAWTs are difficult properly test conventional wind tunnel. Typically Reynolds numbers cannot matched or turbine geometry must altered, limiting applicability results. Presented following is set experiments specialized, high-pressure...

The phenomena of self-sustained shock-wave oscillations over conical bodies with a blunt axisymmetric base subject to uniform high-speed flow are investigated in hypersonic wind tunnel at Mach number $M = 6$ . and dynamics is dictated by two non-dimensional geometric parameters presented the three length scales body, which associated forebody one base. Time-resolved schlieren imagery from these experiments reveals presence disparate states flow, allows for mapping unsteadiness boundaries...

By vibrating a rib, two Fourier modes are injected into turbulent boundary layer. Modes with sum, difference, and double the frequencies detected downstream, their amplitudes across layer investigated.

Experimental studies of the changes in turbulence characteristics inside a boundary layer due to external forcing were performed using hot-wire anemometry. The was created by periodically forced shear that compressible subsonic turbulent layer. convecting coherent structures create concomitant unsteady pressure and velocity field provide an disturbance for on wall tunnel close Both fluctuations simultaneously measured along with signal, phase-locked analysis performed. Regions amplified...

Phase relations between specific scales in a turbulent boundary layer are studied here by highlighting the associated nonlinear scale interactions flow. This is achieved through an experimental technique that allows for targeted forcing of flow use dynamic wall perturbation. Two distinct large-scale modes with well-defined spatial and temporal wavenumbers were simultaneously forced layer, resulting response from their direct was isolated turbulence signal study. approach advances traditional...

Abstract

Flow oscillations in the near-wake region of a 2D circular cylinder are experimentally investigated at Mach 6 over Reynolds number range $2.3\times10^5$ to $5\times10^5$. The oscillation frequency is obtained by spectral proper orthogonal decomposition high-speed schlieren data. Strouhal based on length shear layers found exhibit universal behavior. This corroborates experimental findings 4 from recent literature, and further, behavior also seen hold with respect number. Time-resolved...

A synthetic large-scale motion is excited in a flat plate turbulent boundary layer experiment and its influence on small-scale turbulence studied. The scale seen to alter the average natural phase relationships quasi-deterministic manner, exhibit phase-organizing directly coupled small-scales. results analysis presented here are of interest from scientific perspective, also suggest possibility engineering schemes for favorable manipulation energetic through practical inputs.

This thesis explores the dynamics of scale interactions in a turbulent boundary layer through forcing-response type experimental study. An emphasis is placed on analysis triadic wavenumber since governing Navier-Stokes equations for flow necessitate direct coupling between triadically consist scales. Two sets experiments were performed which deterministic disturbances introduced into using spatially-impulsive dynamic wall perturbation. Hotwire anemometry was employed to measure downstream...

A synthetic spanwise-constant spatio-temporal mode is excited in a flat plate turbulent boundary layer through spatially impulsive patch of dynamic wall-roughness.The streamwise wavelength the approximately corresponds to very large-scale motions present high Reynolds number wall turbulence.Hot wire anemometer measurements made downstream roughness forcing reveal nature two dimensional and its influence on small-scale turbulence.A clear phase organizing effect small-scales noticed presence...

An analytical framework is presented here for estimating the limiting area contraction a family of curved compression ramp (CCR) supersonic air intakes with self-starting capability via overboard spillage. Flow in CCR occurs through combination shock wave and series waves. In general, such offers best features canonical intake families. That is, pressure recovery better than simple (planar ramp) intakes, ratios are Prandtl–Mayer intakes. A modified Kantrowitz criterion startability proposed...