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Article
Publication date: 2 October 2017

Jenq-Muh Hsu, Jui-Yang Chang and Chih-Hung Wang

Named Data Networking (NDN) is a content-centric network differing from the traditional IP-based network. It adopts the name prefix to identify, query and route the information…

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Abstract

Purpose

Named Data Networking (NDN) is a content-centric network differing from the traditional IP-based network. It adopts the name prefix to identify, query and route the information content instead of IP-based addressing and routing. NDN provides a convenient way to access the content without knowing the originated location of the requested information. However, the length of name prefix varies. It is not like the fixed-length IP addresses that makes handling queries or searching the requested information in NDN easier. An efficient name lookup mechanism of name prefix will efficiently increase the performance of prefix identifying, name searching and content retrieving. Therefore, this paper aims to propose a partial name prefix merging and shortening scheme for enhancing the efficiency of name lookup in NDN.

Design/methodology/approach

To reduce the work involved in name prefix identifying, querying, storing and routing, this work adopts a cyclic redundancy check-based encoding scheme to shorten the variable length of the name prefix into a proper and fixed length of encoded numerical information. In fact, the structure of a name prefix is presented in a combination of word segments with the slash symbol. The shortening procedure of name prefix can also be applied to adjacent word segments forming fixed-length encoded data for further efficiently matching the name prefix for name lookup in NDN.

Findings

The experimental results show that the shorter length of encoded name prefix can effectively reduce the access time of name lookup and increasingly retrieve the corresponding named content in NDN. Through partial merging and shortening of name prefix, the length of encoded prefix name may be larger than the whole encoding of name prefix. It retains the information differences from different parts of various name prefixes. Thus, it can avoid collision problems with the same encoded information from various name prefixes.

Originality/value

From the experimental results, it is observed that partial merging and shortening of name prefix is useful for name look up in NDN. It can increase the efficiency of name prefix matching and retrieving in NDN. It can also save memory space to store the name prefix in an NDN node.

Details

Engineering Computations, vol. 34 no. 7
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 26 September 2022

Shiang-Wuu Perng, Horng Wen Wu, Nugroho Putra Kelana, Yi-Ling Guo and Chen-Jui Yang

The purpose of this paper, computational fluid dynamics (CFD) work, is to promote turbulent thermal convection in a heated circular tube using a passive scheme of a slotted…

75

Abstract

Purpose

The purpose of this paper, computational fluid dynamics (CFD) work, is to promote turbulent thermal convection in a heated circular tube using a passive scheme of a slotted twisted sheet.

Design/methodology/approach

The inventive design uses square-cut and conjugate triangular perforations to diversify the twisted tape for better thermal convection. The current novel passive scheme methodology is accomplished by carving the same square cuts and slitting various sizes of equilateral triangle perforations (side length varies between 8 and 16 mm). The re-normalisation group turbulence model and the semi-implicit method for pressure-linked equation method examine the turbulent thermal convection aspects of all simulations at different Reynolds numbers (6,000, 10,000 and 14,000).

Findings

The analyses of simulations exhibit that the placement of a twisted tape with triangle perforations and equidistant square cuts can effectually promote thermal convection in a circular tube. A larger-sized triangle perforation can increase the thermal convection enhancement and thermal performance factor, but an enlarged perforation may decrease the thermal convection enhancement and thermal performance factor. As a result, compared with the smooth circular tube, the circular tube with the slotted twisted sheet slit by a 10 mm equilateral triangle brings about the maximum improvement ratio of the mean Nusselt number of about 2.8 at Re = 6,000. Under weighing the friction through the circular tube, the tube with the slotted twisted sheet slit by a 10 mm equilateral triangle gains the best thermal performance factor of about 1.36 at Re = 6,000.

Research limitations/implications

The working fluid is water and its physical features are assumed to be constant. In addition, the fluid is considered a steady flow in this CFD work.

Practical implications

These CFD predictions will benefit the development of heat exchanger tubes equipped with a slotted twisted sheet to acquire preferable thermal convection enhancement.

Social implications

Higher thermal performance achieved by placing a slotted twisted tape in a heated tube will benefit society in lower energy consumption, machinery maintenance costs and impact on the environment.

Originality/value

This study combined triangle perforations and square cuts on the twisted sheet. This combination can induce the fluid flow across the sheet to disturb the swirling flow and then promote the fluid mixing to increase thermal convection. Therefore, this modified tape can be a profitable passive device for designing a heat exchanger.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 2
Type: Research Article
ISSN: 0961-5539

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