Data from a cliff top radar experiment conducted off the south coast of England are examined in order to investigate applicability three-component model for Doppler spectra, developed using laboratory wavetank data, coastal water sea clutter. This is achieved by detailed analysis prominent features data terms polarisation and characteristics, decorrelation times. confirms presence same Bragg non-Bragg scattering mechanisms as observed wave tank. A dependence each on wind direction can also...

In this study the evolution of initially homogeneous and isotropic turbulence in presence a free surface was investigated. The Navier–Stokes equations were solved via direct pseudo-spectral simulation with resolution 963. Reynolds number based on volume-averaged kinetic energy dissipation rate 147. Periodic boundary conditions used two dimensions, top bottom sides domain flat shear-free. A random, divergence-free velocity field prescribed spectrum as initial condition. An ensemble sixteen...

Two-component laser velocimeter measurements in a fully developed turbulent water channel flow with polymer injection were used to examine the effect of on Reynolds stresses and production terms stress transport equations. These show that while root-mean-square (r.m.s.) fluctuation level streamwise velocity was increased, r.m.s. wall-normal shear reduced. The decrease resulted from altered contributions quadrants (u,v)-plane. Although decreased, magnitude products which most contributed...

A model is presented for the Doppler spectra of low grazing angle radar backscatter from sea surface, and compared with data collected in large wind–wave tank at Ocean Engineering Laboratory (OEL) University California, Santa Barbara (UCSB). The components are based on findings an experiment conducted OEL which synchronous high speed video were recorded, coupled surface slope information gathered using a laser meter. allow clear identification conditions giving rise to Bragg scattering, two...

The thermal design of a power transformer determines its lifetime and loading capability, so correct modelling liquid flow temperature distributions in the winding is vital importance. Existing standards widely used simple calculation models can seriously under/overestimate hotspot temperatures under certain circumstances. In this paper, physical model representing disc-type forced directed cooling mode are investigated experimentally using Particle Image Velocimetry (PIV) measurement system...

Results of an experimental study the interaction a turbulent jet with free surface when issues parallel to are presented. Three different jets, exit velocities and jet-exit diameters, all located two diameters below were studied. At this depth flow, in each case, is fully before significant occurs. The effects Froude number ( Fr ) Reynolds Re investigated by varying velocity diameter. Froude-number identified increasing from = 1 8 at 12700. Reynolds-number 12700 102000 1. Qualitative...

A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations governing equations. methodology supports solutions traditional modeling including such effects as transfer, material decomposition, pyrolysis gas permeation and exchange, thermochemical surface erosion. The scheme uses control-volume approach variable grid to account movement. directly...

Because of their large swath widths about 400-500 km, the ScanSAR modes RADARSAT-1 and -2 Advanced SAR (ASAR) system on Envisat have been preferred operation for hurricane typhoon observations similar applications. While C-band images demonstrated to be well suitable wind retrievals, ocean wave retrievals are a more challenging problem: limited spatial resolution 100 m (RADARSAT)/150 (Envisat), only long waves can get imaged directly, many tropical storm scenarios do not exhibit clear...

Radar backscatter measurements from stationary breaking waves were used to examine how the surface roughness generated by wave affects radar at moderate incidence angles. Stationary submerging a hydrofoil in uniform flow. X band made numerous streamwise positions along an angle of 45° for horizontal transmit and receive polarization (HH) vertical (VV) looking both upwave downwave. The returns increased substantially, HH‐to‐VV ratio approached unity near crests. This signature is consistent...

Paper ageing is an irreversible process, which has made paper insulation a lifetime determining factor for transformers. Chemical indicators in oil such as carbon oxide gases and 2-FAL, are used to indicate the state of it difficult obtain samples measure DP or tensile strength. Methanol amount was recently found be early-ageing indicator paper. In this study, headspace gas chromatography mass spectrometry setup developed methanol transformer oil. This consists auto sampler with tight...

The goals of this study were to develop a set Reynolds-averaged governing equations for turbulent free-surface flow, and use the resulting determine origin surface current in high-Froude-number jet flows. To equations, flow is treated as two-fluid separated by an interface. It shown that general Navier–Stokes written variable property embody field applicable each fluid, well boundary conditions interface and, therefore, can be applied across entire fluid domain, including With starting...

Abstract Accurate river bathymetry characterization is important to understanding all aspects of the riparian environment and provides crucial information for ensuring safe passage vessels guiding channel maintenance operations. Verified models based on readily collected physical data facilitate accurate predictions changes a riverbed caused by traffic, weather, other influences. This paper presents methodology estimating from surface velocity applying variational inverse modeling...

A comprehensive study and assessment of RANS based turbulence models is performed on internal cooling duct passages turbine blades. Conjugate computational heat transfer studies 90 45 degree turbulated ducts are compared to experimental data from the Von Karmon Institute. Spatially resolved Nusselt number distributions computed using CFX in conjunction with several models. In addition, similar a 180 turnaround bend Arizona State University. that experiment, area averaged numbers provided at...

This letter describes a simple model for the backscattered signal received from ocean surface by horizontal-polarization marine radar operating at low grazing angles, including effects of logarithmic amplifiers conventionally used in these radars. Shadowing is accounted via geometric optics. The range dependence mean predicted this compares well with that observed two data sets collected under different environmental conditions. also indicates modulation (the deviation normalized mean)...

Ageing of large transformer fleets is a challenge for utilities. To assess the condition existing fleets, oil commonly tested multiple parameters and data are recorded in databases subsequent interpretation. Through analysing including test results individual details pertaining to UK in-service transformers operating at primary voltage levels 33, 132, 275 400 kV, population analyses revealed generic early degradation phenomenon as indicated by an peak acidity 2-FAL trends with age. By...

Abstract This work describes a phase-resolving wave-forecasting algorithm that is based on the assimilation of marine radar image time series. The tested against synthetic data and field observations. couples X-band observations with wave model uses linear mild slope equations for reconstruction water surface elevations over large domain O (km) prescribed window (min). also enables wave-by-wave forecasting through forward propagation in space time. Marine series provide input previously...

In this study, the interaction with a free surface of an initially axisymmetric jet issuing beneath and parallel to was examined. The purpose determine origin ‘surface current’ – large outward velocity which exists in thin layer adjacent surface. Using equations mean motion, it is shown that near surface, acceleration results from balance between positive contribution lateral Reynolds-stress gradients negative pressure gradient. local field be largely determined by field. Combining these...

Dissolved Gas Analysis (DGA) is one of the most effective methods in condition monitoring and fault diagnosis oil immersed transformers. To facilitate DGA data interpretation, investigation gas generation under laboratory simulated faults using heating method often conducted. However, with method, it difficult to generate a stable thermal temperature above 400°C mineral oil. Therefore this paper introduces an alternative that able up 750°C. The tube based test system described detail...

A Reynolds-stress transport equation model for turbulent drag-reducing viscoelastic flows, such as that which occurs dilute polymer solutions, is presented. The approach relies on an extended set of Reynolds-Averaged Navier-Stokes equations incorporate additional stresses. stresses are specified in terms the mean conformation tensor using FENE-P dumbbell model. solved a coupled manner along with equations. presence motion results explicit equations, well implicit effects pressure-strain...

This paper reports the accumulative effect of multiple negative lightning impulse shots on streamer propagation along liquid/pressboard surface. Pressboards impregnated with insulating liquids including a mineral oil, natural ester and synthetic were tested under point-plane divergent field. Streamer was recorded by high speed intensified CCD camera. In addition, current light signals monitored non-inductive shunt photo multiplier tube (PMT) respectively. It found that 60 s time interval...