scholarly journals Role of Acoustic Streaming in Formation of Unsteady Flow in Billet Sump during Ultrasonic DC Casting of Aluminum Alloys

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3532 ◽  
Author(s):  
Sergey Komarov ◽  
Takuya Yamamoto

The present work investigated melt flow pattern and temperature distribution in the sump of aluminum billets produced in a hot-top equipped direct chilling (DC) caster conventionally and with ultrasonic irradiation. The main emphasis was placed on clarifying the effects of acoustic streaming and hot-top unit type. Acoustic streaming characteristics were investigated first by using the earlier developed numerical model and water model experiments. Then, the acoustic streaming model was applied to develop a numerical code capable of simulating unsteady flow phenomena in the sump during the DC casting process. The results revealed that the introduction of ultrasonic vibrations into the melt in the hot-top unit had little or no effect on the temperature distribution and sump profile, but had a considerable effect on the melt flow pattern in the sump. Our results showed that ultrasound irradiation makes the flow velocity faster and produces a lot of relatively small eddies in the sump bulk and near the mushy zone. The latter causes frequently repeated thinning of the mushy zone layer. The numerical predictions were verified against measurements performed on a pilot DC caster producing 203 mm billets of Al-17%Si alloy. The verification revealed approximately the same sump depth and shape as those in the numerical simulations, and confirms the frequent and large fluctuations of the melt temperature during ultrasound irradiation. However, the measured temperature distribution in the sump significantly differed from that predicted numerically. This suggests that the present mathematical model should be further improved, particularly in terms of more accurate descriptions of boundary conditions and mushy zone characteristics.

2014 ◽  
Vol 794-796 ◽  
pp. 124-129 ◽  
Author(s):  
Sergey Komarov ◽  
Yasuo Ishiwata ◽  
Yoshihiro Takeda

The present work introduces a novel ultrasonic DC casting process which allows producing billets of hypereutectic Al-Si alloys with greatly refined and uniformly distributed particles of primary Si. In the process, ultrasonic vibrations are introduced into an Al-17Si-0.01~0.03P melt in a hot top positioned on the mold by using a high-amplitude ceramic sonotrode. The hot top design and sonotrode arrangement provided a highly effective cavitation treatment of the melt in the hot top and well-controlled flow in the sump. A simplified model is proposed to explain the obtained results.


2012 ◽  
Vol 548 ◽  
pp. 600-604
Author(s):  
Rozana Mohd Dahan ◽  
Saiful Bahri Mohd Yasin ◽  
Zakaria Razak ◽  
Mohd Helmi Omar

Interchangeable Turning Sprue Bushing (ITSB) is a small insert at the centre of core side used to change runner directions for injecting 2 different products in a separate injection mold by shifting the melt filling to the cavities. The development of ITSB is significant in cutting down cost and time consumed during fabrication of a multi cavity family mold. In this study, the tensile and flexural test pieces were designed using CAD Solidwork. The test pieces analysis was performed using CAE Cadmould simulation in order to observe the melt flow of four multi cavities family mold incorporated without and with ITSB insert. The Cadmould simulation was used specifically to analyse the melt filling, temperature distribution and volume shrinkage of the test pieces. The simulation result demonstrated that ITSB is a useful insert that can be used to overcome problems encountered in the family mold system by balancing the melt filling, minimize temperature distribution and reduced the differential of volume shrinkage of the test piece manufactured. ITSB also reduced the frequent defects formed during production such as short molding, flashing and warpage.


Author(s):  
James Y.-K Cho

Tidally synchronized planets present a new opportunity for enriching our understanding of atmospheric dynamics on planets. Subject to an unusual forcing arrangement (steady irradiation on the same side of the planet throughout its orbit), the dynamics on these planets may be unlike that on any of the Solar System planets. Characterizing the flow pattern and temperature distribution on the extrasolar planets is necessary for reliable interpretation of data currently being collected, as well as for guiding future observations. In this paper, several fundamental concepts from atmospheric dynamics, likely to be central for characterization, are discussed. Theoretical issues that need to be addressed in the near future are also highlighted.


2021 ◽  
Vol 2119 (1) ◽  
pp. 012165
Author(s):  
V S Berdnikov ◽  
V A Vinokurov ◽  
V V Vinokurov

Abstract The evolution of the flow structure and heat transfer with an increase in the characteristic temperature drop in the ranges of Grashof and Marangoni numbers 3558 ≤ Gr ≤ 7116 and 2970 ≤ Ma ≤ 5939 are investigated numerically. The boundary of the transition to unsteady flow and heat transfer regimes has been determined.


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