flow visualization techniques using tracer markers such as die, smoke, hydrogen bubbles, etc., have been widely used in experimental investigations of large scale structures of a variety of flow fields. they have played an important role in understanding the physics of the coherent structures formation and evolution in the transitional as well as the turbulent regions of the flow fields. howeve...

hot-wire spirometer uses a constant temperature anemometer (cta) for its operation. the working principle of cta, used for the measurement of fluid velocity and flow turbulence, is based on convective heat transfer from a hot-wire sensor to a fluid being measured. the calibration curve of a cta is nonlinear and cannot be easily extrapolated beyond its calibration range. therefore, a method for ...

A nanoscale thermal anemometry probe (NSTAP) has been developed to measure velocity fluctuations at ultra-small scales. The sensing element is a free-standing platinum nanoscale wire, 100 nm× 2 μm× 60 μm, suspended between two currentcarrying contacts and the sensor is an order of magnitude smaller than presently available commercial hot wires. The probe is constructed using standard semiconduc...

In their recent topical review, Nabavi and Siddiqui (Meas. Sci. Technol. 2010 21 042002) recommended the use of hot-wire anemometry for velocity measurements in pulsating flows, especially at high frequency. This recommendation is misleading. The procedures invoked by these authors are valid only for small-amplitude fluctuations, which are of little interest for pulsating flows. When large-ampl...

Issues concerning the accuracy of hot-wire measurements in turbulent pipe flow are addressed for pipe Reynolds numbers up to 6 × 106 and hot-wire Reynolds numbers up to Rew ≈ 250. These include the optimization of spatial and temporal resolution and the associated feature of signal-to-noise ratio. Very high wire Reynolds numbers enable the use of wires with reduced length-to-diameter ratios com...

In order to express explicitly the effect of the angle-errors of setting a hot-wire probe in a flow field on the output of the hot-wire anemometer, approximate hotwire response series equations based on the small angleerror and weak turbulence approximations (called directionerror response equations in this paper) were derived from I-type, slanted-type and X-type hot-wire probes in twodimension...

Hot-wire measurements have been made in the boundary layer, the separated region, and the near wake for flow past an NACA 4412 airfoil at mad mum lift. The Reynolds number based on chord was about 1,500,000. Special care was taken to achieve a two-dimensional mean flow. The main instrumentation was a flying hot wire; that is, a hot-wire probe mounted on the end of a rotating arm. The probe velo...

Adjacent parallel hot-wire anemometers at different temperatures have sometimes been used to measure fluctuating temperatures in turbulent flows. This work presents an extensive experimental comparison of temperatures measured with a parallel-wire probe to temperatures simultaneously measured with a standard cold-wire probe. The results show the parallel-wire probe to work well in low intensity...

Abstract Hot-wire laser welding is additive manufacturing (AM) technique that allows for the direct creation of complicated objects by melting layers wire. This process characterized use hot-wire process, unification with (LW) in AM process. The empirical investigation employing a on titanium alloy (grade 2) workpiece presented this research. There are three parameters namely wire current, spee...