Flow characteristic of highly underexpanded jets from various nozzle geometries
TL;DR: In this article, the authors studied the flow characteristics of highly underexpanded jets at the same nozzle pressure ratio of 5.60 but issuing from four different nozzles, i.e., the circular, elliptic, square, and rectangular jets, and showed that the square jet penetrates fastest, although the turbulence transition is similar for different jets.
About: This article is published in Applied Thermal Engineering.The article was published on 2017-10-01 and is currently open access. It has received 43 citations till now. The article focuses on the topics: Shock diamond & Mach reflection.
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TL;DR: In this paper, the signature of an aeroacoustic resonance loop established by a shock-containing jet is described, and the resonance loop can be used to identify the origin of high-intensity, discrete-frequency acoustic tones.
Abstract: Supersonic jets, particularly shock-containing jets, often exhibit high-intensity, discrete-frequency acoustic tones. These tones are the signature of an aeroacoustic resonance loop established by ...
136 citations
TL;DR: In this paper, the authors explored the basic characteristics of the underexpansion jet flame in premixed H2/air explosion venting, and discussed the formation of two under-expansion structures (Mach disk and diamond shock wave) of such jet flames.
71 citations
TL;DR: This paper investigates the properties of 3D printed fibre-reinforced cementitious mortar prisms and members in conjunction with automation to achieve the optimum mechanical strength of printed mortar and to obtain suitable flowability and consistent workability for the mixed cementitious bricks during the printing process.
Abstract: Recently, 3D printing has become one of the most popular additive manufacturing technologies. This technology has been utilised to prototype trial and produced components for various applications, such as fashion, food, automotive, medical, and construction. In recent years, automation also has become increasingly prevalent in the construction field. Extrusion printing is the most successful method to print cementitious materials, but it still faces significant challenges, such as pumpability of materials, buildability, consistency in the materials, flowability, and workability. This paper investigates the properties of 3D printed fibre-reinforced cementitious mortar prisms and members in conjunction with automation to achieve the optimum mechanical strength of printed mortar and to obtain suitable flowability and consistent workability for the mixed cementitious mortar during the printing process. This study also considered the necessary trial tests, which are required to check the mechanical properties and behaviour of the proportions of the cementitious mix. Mechanical strength was measured and shown to increase when the samples were printed using fibre-reinforced mortar by means of a caulking gun, compared with the samples that were printed using the same mix delivered by a progressive cavity pump to a 6 degree-of-freedom robot. The flexural strength of the four-printed layer fibre-reinforced mortar was found to be 3.44 ± 0.11 MPa and 5.78 ± 0.02 MPa for the one-layer. Moreover, the mortar with different types of nozzles by means of caulking is printed and compared. Several experimental tests for the fresh state of the mortar were conducted and are discussed.
54 citations
Cites background from "Flow characteristic of highly under..."
...[37] asserted that intercepting shocks are significantly changed according to the shape of the nozzles....
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TL;DR: In this paper , the formation of the underexpansion jet flame (UEJF) of premixed hydrogen/air in explosion venting was simulated by ANSYS Fluent, and the wave system structures of the UEJF were systematically analyzed.
50 citations
TL;DR: In this paper, a density-based solver for compressible supersonic flow, astroFoam, is developed based on the OpenFOAM library, which performs large-eddy simulations of highly underexpanded jets with nozzle pressure ratios from 5.60 to 11.21 at a Reynolds number around 105.
Abstract: High-pressure jet injection into quiescent air is a challenging fluid dynamics problem in the field of aerospace engineering. Although plenty of experimental, theoretical, and numerical studies have been conducted to explore this flow, there is a dearth of literature detailing the flow evolution and instability characteristics, which is vital to the mixing enhancement design and jet noise reduction. In this paper, a density-based solver for compressible supersonic flow, astroFoam, is developed based on the OpenFOAM library. Large-eddy simulations of highly underexpanded jets with nozzle pressure ratios from 5.60 to 11.21 at a Reynolds number around 105 are carried out with a high-resolution grid. A grid-convergence study has been conducted to confirm the fidelity of the large-eddy simulation results. The large-eddy simulation results have also been validated against available literature data in terms of the time-averaged near-field properties of underexpanded jets. The turbulent transition processes are r...
46 citations
References
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Book•
01 Jan 1966
3,520 citations
"Flow characteristic of highly under..." refers methods in this paper
...per unit mass hk and the specific heat at constant pressure cpk, are calculated based on NIST-JANAF thermo-physical and transport database [38]....
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TL;DR: It is proved that a scalar version of the high-resolution central scheme is nonoscillatory in the sense of satisfying the total-variation diminishing property in the one-dimensional case and the maximum principle in two-space dimensions.
1,685 citations
"Flow characteristic of highly under..." refers methods in this paper
...In astroFoam, the convection-diffusion equation is solved by semi-discrete KT (Kurganov and Tadmor) scheme [39] for shock capturing and turbulence resolving....
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Journal Article•
859 citations
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795 citations
"Flow characteristic of highly under..." refers background in this paper
...The acoustic waves that originate around the end of jet potential core propagate both upstream and downstream [51]....
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TL;DR: In this article, the mean properties of the flow field are established for three types of jet flow issuing from a circular convergent nozzle, and measured distributions of surface pressure are given which result when the jets impinge both normally and obliquely at various distances on several surface shapes.
Abstract: In this, the first part of a two-part experimental study of the behaviour of impinging jets, the mean properties of the flow field are established. Velocity profiles are given for three types of jet flow issuing from a circular convergent nozzle. Measured distributions of surface pressure are given which result when the jets impinge both normally and obliquely at various distances on several surface shapes. The pressure distributions are used to compute the radial velocity gradient at the impingement stagnation point. It is found that for normal impingement this gradient correlates with the free jet centreline velocity and half-radius at the same axial location. A fall-off in the correlated value is noted as the impingement is made oblique. Measurements of the azimuthal distribution of momentum flux in the resulting wall jet are also given. The general behaviour of all three types of jet is found to be similar at locations downstream of any local effects due to the shock waves present in the under-expanded types. A special study of the close-range impingement of an under-expanded jet containing a normal shock disk reveals a region of separated flow surrounding the stagnation point. This condition results in a negative value of the radial velocity gradient at the centreline.
549 citations