Numerical analysis of unstable turbulent flows in a centrifugal pump impeller considering the curvature and rotation effect

Weixiang Ye,Zu-chao Zhu,Zhong-Dong Qian,Xianwu Luo 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.7

In this study, a modified partially averaged Navier–Stokes model (MSST PANS) is proposed by treating a modified shear stress transport (SST) k–ω model as the parent turbulence model. The unstable turbulent flow in a centrifugal pump that considers the curvature and rotation effect is investigated as the test case to evaluate the performance of the MSST PANS model and analyze the flow instability in a centrifugal pump. The SST k–ω and the standard k–ε PANS models are also evaluated for comparison. Results show that the MSST PANS model exhibits excellent performance and delivers the most satisfactory prediction results of the positive slope of the characteristic curve, time-averaged internal flows, and velocity profiles. The energy loss based on the energy balance equations is adopted to provide an explanation of the internal flow evolutions in pumps. The findings also indicate energy loss distribution is associated with the positive slope phenomenon. The high-velocity gradient flows at the entrance of the blade-toblade passage and the reverse flows at the impeller exit are the main reasons for the high turbulent kinetic energy in the impeller. The MSST PANS model demonstrates promising applications in the field of hydraulic machinery, where unstable turbulent flows are prevalent.

Instability analysis under part-load conditions in centrifugal pump

Weixiang Ye,Renfang Huang,Zhiwu Jiang,Xiaojun Li,ZuChao Zhu,Xianwu Luo 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1

In this study, a centrifugal pump with a specific speed of 39.12 m×min -1 ×m 3 s -1 is treated to analyze the flow instability under part-load conditions by numerical simulation and experimental test. For calculations, the RANS method, coupled with the k-ω SST turbulence model, is adopted. Numerical results at different operation points are compared with available experimental data, such as hydraulic performance and flow field information by particle image velocimetry. The numerical and experiment results agree well. The flow simulation indicates a strong reverse flow at the passage upstream impeller inlet, and the energy loss in the impeller is the largest under partload conditions among all flow components in the pump. In one impeller revolution, one blade-to-blade flow passage is always nearly blocked off by the rotating stall occurring at the impeller inlet for each instant, and the blockage induces a jet flow with large velocity at the next blade-to-blade flow passage along the rotational direction of the impeller. The blockage and the jet flow in the blade-to-blade flow passages will make the flow unstable inside the impeller and cause performance breakdown and pressure vibration under part-load conditions for the pump.

Research on an Approach of Cloud Workloads Deployment to Public Cloud Based on Open Source Standard

Xu Weixiang,Jia Lin 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.3

Cloud computing is a kind of formula mode that is based on internet, and in this way, the sharing software and hardware resource and information can be provided for the computer and the other terminal devices on demand. However, due to technical differences among main service vendors, there is a compatibility issue on appropriate format that is based on the virtual machine manager of different cloud platforms. Therefore, it brings some hinder to flexible deployment of cloud workloads to some extent. While with the great development of open source standers, such issues can be solved in another train of thought. In this paper, it proposes a constructive solution to deploy cloud workloads based on open source standers. In the whole structure, the key point is that a cloud middleware is introduced and the application of MapReduce algorithm. The cloud middleware contains four kinds of modules, namely, OVF converter, classifier, interface matched and security check. And the improved MapReduce algorithm is used to the classification phase of the cloud workloads. In the program, cloud workloads are sent to the cloud middleware, and in the process of "classified → packaged →matching interface → security check → deployment", which can make cloud workloads deployed easily and flexibly. And this paper will elaborate the progress of each section through a theory case. The biggest construction of this program is manifested in four aspects that are function modular, operation independence, security and scalability. This program must be further improvement, based on the addition of functional roles and the development of open source standards, and has a strong theoretical and practical significance.

Improved Computing Method of Mutual Information in Medical Image Registration

Xumin Liu,Zilong Duan,Weixiang Xu 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.4

Mutual information based medical image registration is one of the most common registration method in registration domain currently. This paper studies the mutual information of the calculation process for mutual information calculation speed is slow, low efficiency of registration, registration can not meet real-time requirements, an improved gray compression algorithm, by reducing the gray-scale of images to improve image the registration efficiency and gradient similarity combined with mutual information as a new registration measure, so that the registration in improving efficiency while meeting the requirement of registration accuracy. The comparative experiments this article made show that, under the premise of registration accuracy to ensure that the method can significantly improve the speed of image registration.

Vector Quantization Method Based on Satellite Cloud Image

Xumin Liu,Zilong Duan,Xue Yang,Weixiang Xu 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.11

Automatic vectorization in the field of image processing and recognition is one of development direction. This paper does some relevant researches on satellite cloud image preprocessing, image segmentation, image vector quantization. To improve the effect of noise reduction and preserving image details, this paper puts forward an improved adaptive median filter algorithm; For increasing the speed of image segmentation, this paper puts forward automatic layering algorithm combined with color information. Finally, this paper puts forward automatic vector quantization algorithm based on satellite cloud images and we developed an automatic vector quantization prototype system of satellite cloud images. The research results suggest that our automatic vector quantization algorithm has satellite cloud information automatic extraction function, identification function and vector quantization function.

Research on 3D Visualization Method of Seismic Data

Xumin Liu,Dawei Li,Yongxiu Xu,Weixiang Xu 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.5

3D visualization is an important link in seismic data processing and interpretation, and the development of the microcomputer system of 3d visualization software for seismic data is very necessary. This paper uses MFC (Microsoft Programming Interface) and VTK (Visualization Toolkit) building three-dimensional scene, realizing the 3d seismic data field Visualization display system and determining the projection window according to characteristics of the seismic data field which is a regular three-dimensional spatial data field. In this paper, we apply the 3d visualization technology to the field of seismic data processing, use the improved light projected volume rendering method to directly render 3d seismic data and displaying the 3d seismic data to users in the form of three-dimensional interpretation, greatly improve the efficiency and accuracy of seismic interpretation, at the same time, also can provide a powerful conditions for further data interpretation and analysis.

Vectorization Method on the Color Cloud Image

Xumin Liu,Cong Zhang,Sen Na,Weixiang Xu 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.12

Flexible Plate Teeth Type Sugarcane Leaf-Stripping Device

Xin Jin,Xinwu Du,Dongyang Wang,Weixiang Liu,Jiangtao Ji 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.9

An Image Edge Detection Algorithm Based on Improved Wavelet Transform

Xumin Liu,Zilong Duan,Xiaojun Wang,Weixiang Xu 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.4

In this paper, for wavelet modulus maxima edge detection affected by noise largely, we propose an improved image fusion algorithm. Firstly, wavelet denoising and smoothing filter are conducted on the original image. Secondly, making edge detection with wavelet transform modulus maxima edge detection and improved canny edge detection get each of edge detection images. Thirdly, let the wavelet fusion follow some certain fusion rules. Finally, making the inverse wavelet transform reconstruct the fused image. The experimental results show that the fused image combines the advantages of edge detection methods, which is an effective image edge detection method.

Validation of a Risk Score Incorporating Tumor Characteristics into the American Joint Committee on Cancer Anatomic Stage for Breast Cancer

Yi Heng Seow,Ru Xin Wong,John Heng Chi Lim,Weixiang Lian,Yoon Sim Yap,Fuh Yong Wong 한국유방암학회 2019 Journal of breast cancer Vol.22 No.2

Purpose: The American Joint Committee on Cancer 8th edition (AJCC8) prognostic stage (PS) was implemented January 1, 2018, but it is complex due to multiple permutations. A North American group proposed a simpler system using the anatomic stage with a risk score system (RSS) of 1 point each for grade 3 tumor and human epithelial growth factor receptor 2 (HER2) and estrogen receptor (ER) negativity. Here we aimed to evaluate this risk score system with our database of Asian breast cancer patients and compare it against the AJCC8 PS. Methods: Patients diagnosed with breast cancer stage I–IV in 2006–2012 were identified in the SingHealth Joint Breast Cancer Registry. Five-year breast cancer-specific survival (CSS) and overall survival (OS) were calculated for each anatomic stage according to the risk score and compared with the AJCC8 PS. Results: A total of 6,656 patients were analyzed. The median follow-up was 61 (interquartile range, 37–90) months. There was a high receipt of endocrine therapy (84.6% of ER+ patients), chemotherapy (84.3% of node-positive patients), and trastuzumab (86.0% of HER2+ patients). Within each anatomic stage, there were significant differences in survival in all sub-stages except IIIB. On multivariate analysis, the hazard ratio for negative ER was 1.74 (1.48–2.06), for negative HER2 was 1.49 (1.26–1.74), and for grade 3 was 1.84 (1.55–2.19). On multivariate analysis controlled for age, ethnicity, and receipt of chemotherapy, the RSS (Akaike information criterion [AIC] = 10,649.45; Harrell's Concordance Index [C] = 0.85) was not inferior to the AJCC8 PS (AIC = 10,726.65; C = 0.84) for CSS, nor was the RSS (AIC = 14,714.4; C = 0.82) inferior to the AJCC8 PS (AIC = 14,784.69; C = 0.81) for OS. Conclusion: The RSS is comparable to the AJCC8 PS for a patient population receiving chemotherapy as well as endocrine- and HER2-targeted therapy and further stratifies stage IV patients.