The effect of low Reynolds number flows on pitot tube measurements

Spelay, Ryan B.; Adane, Kofi Freeman; Sanders, R. Sean; Sumner, Robert J.; Gillies, Randall G.

doi:10.1016/j.flowmeasinst.2015.06.008

Cited by 20 publications

(7 citation statements)

References 19 publications

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“…For this study, the gas flow was monitored with an intrusive velocity measurement instrument known as a Pitot tube. It works as a differential pressure anemometer that allows the velocity measurement of a single localized fluid flow [22]. Practically, such a device, widely used to measure aircraft's speed, is made of a tube with an open end facing the fluid flow (total pressure entrance) and an orifice flush tangential to the tube, which registers the static pressure [23].…”

Section: Gas Velocity Measurementmentioning

confidence: 99%

“…However, their accuracy can be limited for unsteady flows, especially when the viscous effects become too significant (low Reynolds number). Studies by Spelayet al [22] and Boetcher et al [25] showed that pitot measurement conducted with a Reynolds number lower than 100 could not be accurately predicted with Bernoulli's method and needs correlation terms to correct it. In this study, the Reynolds numbers of each gas flow coming out from the three studied nozzles are higher than 1000 for the usual gas process parameters, meaning that the basic Bernoulli's equation is sufficient to describe the speed flow.…”

Section: Gas Velocity Measurementmentioning

confidence: 99%

See 1 more Smart Citation

Experimental and Numerical Analysis of Gas/Powder Flow for Different LMD Nozzles

Ferreira

Dal

Colin

et al. 2020

Metals

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The Laser Metal Deposition (LMD) process is an additive manufacturing method, which generates 3D structures through the interaction of a laser beam and a gas/powder stream. The stream diameter, surface density and focal plan position affect the size, efficiency and regularity of the deposit tracks. Therefore, a precise knowledge of the gas/powder streams characteristics is essential to control the process and improve its reliability and reproducibly for industrial applications. This paper proposes multiple experimental techniques, such as gas pressure measurement, optical and weighting methods, to analyze the gas and particle velocity, the powder stream diameter, its focal plan position and density. This was carried out for three nozzle designs and multiple gas and powder flow rates conditions. The results reveal that (1) the particle stream follows a Gaussian distribution while the gas velocity field is closer to a top hat one; (2) axial, carrier and shaping gas flow significantly impact the powder stream’s focal plan position; (3) only shaping gas, powder flow rates and nozzle design impact the powder stream diameter. 2D axisymmetric models of the gas and powder streams with RANS turbulent model are then performed on each of the three nozzles and highlight good agreements with experimental results but an over-estimation of the gas velocity by pressure measurements.

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Section: Gas Velocity Measurementmentioning

confidence: 99%

Section: Gas Velocity Measurementmentioning

confidence: 99%

Experimental and Numerical Analysis of Gas/Powder Flow for Different LMD Nozzles

Ferreira

Dal

Colin

et al. 2020

Metals

View full text Add to dashboard Cite

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“…However, both results describe a velocity field with the same shape, i.e., describing a hat top function. Flow velocity measurements using a Pitot tube, based on the Bernoulli equation is more appropriate for flows with higher Reynolds number (16). In low Reynolds number, the viscosity has a strong effect on the flow pattern, therefore limiting the use of the Bernoulli equation.…”

Section: Resultsmentioning

confidence: 99%

Numerical and Experimental Analysis of Gas Flow in a Coaxial Nozzle Applied to Directed Energy Deposition (DED)

Nunez

Perilla

Rios

et al. 2021

IJEMM

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create a melt pool on the substrate. A nozzle is used to carry metal powder within a gas flow until the melt pool, concentrating the flow at the same point. Coaxial nozzles usually have also a shield gas flow to prevent oxidation and an internal flow to protect the optical system. A right flow configuration must be selected to avoid high turbulence at the nozzle exit, leading to an efficient, inexpensive, and high-quality process. Due to the complexity of the process, CFD – Computer Fluid Dynamics are becoming necessary to understand the behaviour of those gas flows in DED processes. CFD can offer results close to reality and may allow an optimization of the whole nozzle designs, besides selecting the best gas flows for each application. The present work develops a CFD simulation of the gas flow behaviour in a coaxial nozzle with three internal annular channels (internal, carrier and shield). An initial set of gas flow was selected, based on previous experience of the manufacturer, and then improved. It searches for the low gas consumption, to form a focal point coinciding with the laser focus and a low velocity, which favours the deposition quality. To check the accuracy of the proposed CFD model, experimental measurements of gas velocity were performed and compared with simulated results.

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“…. (6) where e r and e z are the unit vectors of the velocity components u r and u z , respectively. Because the ∇ operator acts on the vector field u, the dot or scalar product results in a divergence, and Equation 2 eventually yields in…”

Section: Governing Equationsmentioning

confidence: 99%

“…The results indicated a good match between experimental data and theoretical predictions. The effect of low Reynolds number (Re) on hemispherical-tipped Pitot tube measurements was analysed in Spelay et al (6) Empirical correlations, considering an additional viscous term, were obtained for several diameter ratios. They also obtained a new value of Re for a transaction regime in the PP.…”

Section: Introductionmentioning

confidence: 99%

Numerical and experimental characterisation of an aeronautic Pitot probe

et al. 2019

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Aeronautic Pitot probes (PPs) are extremely important for airspeed and altitude measurements in aviation. Failure of the instrument due to clogging caused by ice formation can lead to dangerous situations. In this work, a commercial aeronautic PP was characterised experimentally regarding its inner composition, material properties and its thermal performance in a climatic wind tunnel. Performance runs were taken out in order to analyse the thermal response of the PP under various operating conditions with a particular emphasis on the cooling process in the case of a heating element failure. Data for the thermal conductivity, diffusivity and specific heat for each material forming the PP were obtained. A numerical model to simulate the thermal behaviour of the PP was created using Comsol Multiphysics (CM). Experimental data were compared with their numerical counterparts for model validation purposes. After the model was validated, the operation of the PP in flight conditions was simulated. The failure of the conventional heating system was analysed to obtain the time until the PP reaches a tip temperature where ice formation can be expected. The tip temperature undercut the zero degrees Celsius mark 165 seconds after the heating element was switched off. The data collected in this work can be used to implement and validate mathematical models in order to predict the thermal performance of Pitot probes in flight conditions.

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The effect of low Reynolds number flows on pitot tube measurements

Cited by 20 publications

References 19 publications

Experimental and Numerical Analysis of Gas/Powder Flow for Different LMD Nozzles

Experimental and Numerical Analysis of Gas/Powder Flow for Different LMD Nozzles

Numerical and Experimental Analysis of Gas Flow in a Coaxial Nozzle Applied to Directed Energy Deposition (DED)

Numerical and experimental characterisation of an aeronautic Pitot probe

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