Natural convection in Bingham plastic fluids from an isothermal spheroid: Effects of fluid yield stress, viscous dissipation and temperature-dependent viscosity

Anoop Kumar Gupta,Sanjay Gupta,Rajendra Prasad Chhabra 한국유변학회 2017 Korea-Australia rheology journal Vol.29 No.3

In this work, the buoyancy-induced convection from an isothermal spheroid is studied in a Bingham plastic fluid. Extensive results on the morphology of approximate yield surfaces, temperature profiles, and the local and average Nusselt numbers are reported to elucidate the effects of the pertinent dimensionless parameters: Rayleigh number, 102 ≤ Ra ≤ 10 6; Prandtl number, 20 ≤ Pr ≤ 100; Bingham number, 0 ≤ Bn ≤ 10 3, and aspect ratio, 0.2 ≤ e ≤ 5. Due to the fluid yield stress, fluid-like (yielded) and solid-like (unyielded) regions coexist in the flow domain depending upon the prevailing stress levels vis-a-vis the value of the fluid yield stress. The yielded parts progressively grow in size with the rising Rayleigh number while this tendency is countered by the increasing Bingham and Prandtl numbers. Due to these two competing effects, a limiting value of the Bingham number (Bnmax) is observed beyond which heat transfer occurs solely by conduction due to the solid-like behaviour of the fluid everywhere in the domain. Such limiting values bear a positive dependence on the Rayleigh number (Ra) and aspect ratio (e). In addition to this, oblate shapes (e < 1) foster heat transfer with respect to spheres (e = 1) while prolate shapes (e > 1) impede it. Finally, simple predictive expressions for the maximum Bingham number and the average Nusselt number are developed which can be used to predict a priori the overall heat transfer coefficient in a new application. Also, a criterion is developed in terms of the composite parameter which predicts the onset of convection in such fluids. Similarly, another criterion is developed which delineates the conditions for the onset of settling due to buoyancy effects. The paper is concluded by presenting limited results to delineate the effects of viscous dissipation and the temperature-dependent viscosity on the Nusselt number. Both these effects are seen to be rather small in Bingham plastic fluids.

Anomalously high dielectric strength and low frequency dielectric relaxation of a bent-core liquid crystal with a large kink angle

Anoop Kumar Srivastava,김종윤,여성구,정진영,최이준,SINGHVIJAY,이지훈 한국물리학회 2017 Current Applied Physics Vol.17 No.6

We investigated the dielectric dispersion property of a bent-core liquid crystal (BLC) with a large kink angle in the frequency range of 1.0 Hze5.5 MHz in a planar aligned cell. Single dielectric dispersion was observed in the smectic A, nematic, and isotropic phase of the planar aligned sample. The dielectric strengths, relaxation frequencies, distribution parameters, and dc conductivity were measured as a function of temperature. The dielectric strength of the observed relaxation mode was anomalously high (~70), whereas the relaxation frequency was low at ~500 Hz. The relaxation mode observed in the planar aligned cell was attributed to the fluctuations in the polarization direction due to the cooperative motion of the molecules.

Negative dispersion retarder using two negative birefringence films

Srivastava, Anoop Kumar,Yang, Seungbin,Lee, Ji-Hoon The Optical Society 2015 Optics express Vol.23 No.10

A parametric study of the 2D model of solar air heater with elliptical rib roughness using CFD

Rajneesh Kumar,Varun Geol,Anoop Kumar 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2

The heat transfer can be improved by providing artificial roughness on absorber plate of the solar air heat. Many studies are available on circular, semi-circular, triangular and rectangular rib roughened solar air heater. But in present study heat transfer enhancement by providing elliptical ribs on absorber plate was analyzed by developing CFD code on non-commercial ANSYS (Fluent) 12.1 software. The simulations were performed on 2-D CFD model and analysis was carried out to study the effect of relative roughness width, relative roughness height and relative roughness pitch on heat transfer and friction factor. The Reynolds number range from 4000 to 15000 and turbulence phenomena is modeled by using Reynolds-average Navier-Stokes equations (RANS). The mathematical modeling is validated and compared with available results. The strong vortex formation takes place in the main stream flow because of elliptical roughness, which improved heat transfer augmentation in the solar air heater. The local turbulence kinetic energy strongly influenced by orientation of the elliptical ribs. The value of average Nusselt number increases by increasing relative roughness height but it decreases with the increase of relative roughness width and relative roughness pitch. The rib width has significant effects on heat transfer enhancement and maximum Nusselt number is observed for relatively small roughness width (i.e., 0.5) among the considered range of 0.5 mm to 2.0 mm. The maximum value of Nusselt number and friction factor is observed for relative roughness width of 0.5, relative roughness height of 0.045, and relative roughness pitch of 6.

Adaptation of block chain technology in SCM for steering managerial strategies: investigative study under Indian context

Atul Kumar Sahu,Abhijeet Katyayan,Umesh Khandey,Prashant Jangde,Anoop Kumar Sahu,Nitin Kumar Sahu 인하대학교 정석물류통상연구원 2023 JOURNAL OF INTERNATIONAL LOGISTICS AND TRADE Vol.21 No.1

Purpose – Block chain technology (BCT) has apparent capability of handling information in digital format, which has dragged attention of the practitioners for its utility in industrial and manufacturing practices. Conversely, the managerial adoption of BCT is relatively limited, which motivated the authors to identify crucial dimensions that can persuade the acceptance of BCT from an executive perspective. Thus, the present study is aimed to conduct to understand crucial barriers under BCT for managerial implementation in supply chain management (SCM) of small and medium enterprises (SMEs). Design/methodology/approach – The present study investigated evident barriers to understand implementation of BCT. A questionnaire based survey is performed to collect primary data from service and manufacturing based companies in India. Survey responses are received online and the data is analyzed in a scorecard. The scorecard embedded the scribed entries of Likert scale to determine the relative score. Findings – In present study, sixteen barriers from three categories named as technological, organizational and environmental are evaluated, where, five sub-barriers from technological domain, seven sub-barriers from organizational domain and four sub-barriers from environmental domain are evaluated. The findings of the study determined that the three factors, i.e. “complexity in setup/use”, “Security and privacy concern” and “Technological awareness” mostly affect the adaptation of BCT in SCM. Conversely, “Market dynamics”, “Scalability” and “Cost” do not influence the intention to adopt the technology. Originality/value – Only few studies have endeavored to ascertain the BCT adoption in SCM of SMEs in developing country like India. Thus, the study is filling a momentous gap of mapping BCT dimensions in the scholastic literature. The findings are expected to enable SMEs to understand important factors to be considered for adopting BCT in their curriculum. Furthermore, the study may benefit the BCT developers and suppliers to endure customized solutions based on the findings.

Electrokinetic Study and Surface Conductance of Carbon Nanotubes in Liquid Crystal Medium

Srivastava, Anoop Kumar,Pandey, Avinash C.,Kripal, Ram,Lee, Seung Hee Taylor Francis 2014 SOFT MATERIALS Vol.12 No.3

Numerical investigation of heat transfer and friction factor in ribbed triangular duct solar air heater using Computational fluid dynamics (CFD)

Rajneesh Kumar,Varun Goel,Anoop Kumar,Sourabh Khurana,Paramvir Singh,Santosh B. Bopche 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.1

The Computational fluid dynamics (CFD) based analysis is carried out to investigate the thermal and hydraulic performance of circular rib roughened triangular passage Solar air heater (SAH). The circular ribs were provided over the absorber plate. The roughness parameter such as relative roughness pitch (P/e) and relative roughness height (e/D) varies from 4 to 20 and 0.015 to 0.06 (in four sets), respectively, the Reynolds number (Re) varies from 4000 to 18000. The flow governing equations were solved using commercial ANSYS (Fluent) software. The predicted Nusselt number (Nu) and friction factor (f) are validated with the available experimental results. The thermal and hydraulic performance of roughened duct is estimated in the form of Nusselt number and friction factor, respectively. The Thermohydraulic performance parameter (TPP) is also evaluated depending on the friction factor (f) and Nusselt number (Nu) values for SAH. The maximum Thermohydraulic performance parameter (TPP) is observed at Reynolds number of 15000 in case of relative roughness pitch (P/e) and relative roughness height (e/D) value of 12 and 0.06, respectively.

In Depth Analysis of Attacks & Countermeasures in Vehicular Ad Hoc Network

Naziya Hussain,Anoop Singh,Piyush Kumar Shukla 보안공학연구지원센터 2016 International Journal of Software Engineering and Vol.10 No.12

A vehicular ad hoc networks (VANETs) communication is becoming an important and popular research factor in the wireless networking. It has the potential to improve road safety and travelers comfort. VANETs are distributed, self-organizing communication networks built by moving vehicles. Its differ from MANET by their architecture, characteristics and applications as well as some sort of security issues. A vehicular ad hoc network (VANETs) is very important factor for improving the road safety and comforting of the travelers. Recently VANETs have emerged to turn the attention of researchers in the field of wireless and mobile communications; they differ from MANET by their architecture, characteristics and applications as well as some sort of security issues which make them to the deployment stage, potential security and privacy issues must be addressed. It’s associate spontaneous network for the longer term Intelligent Transport System (ITS) sensible progress achieved by the investigator on study of Vehicular Ad hoc Network. However some challenges and problems still here for analysis is to be like communication, security, application, stimulation, verification and services. These solutions is classified into Public-Key Approaches, Symmetric; Hybrid Approaches and ID based mostly having the aim to construct a strong security framework for VANETs and thereby stop security attacks considerately to adapt with specific options of VANETs. In this paper we have a tendency to present the maximum aspects alongside the comparison associated with this field to assist researchers and developers to know and distinguish the most surrounding VANET in one solid document, while not the necessity to travel through different relevant papers and articles preliminary from VANET architecture by gaging up with the improving productivity of node compromise attack in vehicular Ad hoc network using Connected Dominating Set recommended general algorithmic program, that promotes the attacking productivity by destroying the network backbone and Analysis of Novel & Empirical Methods Explained Attacks & Countermeasures in Vehicular Ad Hoc Network.

Temperature Dependence of the Electro-optic Characteristics in the Liquid Crystal Display Switching Modes

전은정,이승희,Anoop Kumar Srivastava,김미영,정광운,최정민,이기동 한국정보디스플레이학회 2009 Journal of information display Vol.10 No.4

As the physical properties of nematic liquid crystals vary with respect to temperature, the performances of liquid crystal displays (LCDs) are highly dependent on temperature. Additionally, it is well known that the electro-optic characteristics of LCDs, such as transmittance and threshold voltage, also rely on the LCD switching modes. The temperature dependence of the electro-optic characteristics of the wide-viewing-angle LCD modes, such as in-plane switching (IPS), multidomain vertical alignment by patterned electrode (PVA), and fringe-field switching (FFS), have been studied, and the results showed that the FFS mode has lower temperature dependence compared to the IPS and PVA modes. Since the liquid crystal (LC) reorients in different ways in each mode, this result is associated with the temperature dependence of LC’s bend and twist elastic constants, and also with the position of the main reorientation, either in the middle or on the surface of the LC layer.

Temperature Dependences of the Electrooptical Properties of Rodlike Nematic Liquid Crystals Doped with Hockey-stick-shaped Liquid Crystals

Sunggu Yeo,Anoop Kumar Srivastava,Hyojin Lee,Ji-Hoon Lee,E-Joon Choi 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.2

We investigated the temperature dependences of the dielectric anisotropy, birefringence, order parameter, splay elastic constant, and rotational viscosity of rodlike nematic liquid crystals (RLCs) doped with hockey-stick-shaped liquid crystals (HLCs). Although the order parameter of the HLCRLC mixtures was similar to that of the pure RLC, the dielectric anisotropy and the birefringence of the mixtures were decreased or increased depending on the structure of the HLC molecule. In addition, the activation energies of the mixtures were different, which implies that the intramolecular structure of the HLC molecule had more influence on the electrooptical properties of the HLC-RLC binary mixtures than the inter-molecular interaction between the HLC and the RLC molecules.