Vagesh D. Narasimhamurthy

Bio: Vagesh D. Narasimhamurthy is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Reynolds number & Turbulence. The author has an hindex of 11, co-authored 46 publications receiving 455 citations. Previous affiliations of Vagesh D. Narasimhamurthy include Norwegian University of Science and Technology.

DNS of turbulent flow in a rotating rough channel

Abstract: All solid surfaces in practice can be considered rough to a certain degree and this surface roughness is known to affect the fluid flow to a considerable extent. It is also known from the literature that system rotation affects both the mean fluid motion and the turbulence. Fluid flows involving both the surface roughness and the system rotation are therefore of major concern in industrial, geophysical and astrophysical applications.

Perforated Bluff-Body Wake Simulations: Influence of Aspect Ratio

Abstract: Parallel computations of flow past a perforated plate of porosity 25% at Reynolds number 250 (based on plate width, d and inflow velocity, Uo) is carried out. The effect of aspect ratio is studied with different span-wise lengths of the domain (1d, 3d and 6d). Present results revealed that an aspect ratio of 6d is required to capture the transient wake dynamics. It was found that statistical quantities stemming from aspect ratio 3d and 6d cases agree with each other, though the dynamical behavior of the wake is very different. The signature period doubling effects associated with short constrained domains were visible in the 1d and 3d aspect ratio cases. Enforcing periodic boundary condition along the short span-wise domains may thus adversely affect the flow.

Aspects of a turbulent-nonturbulent interface

Abstract: Transport mechanisms at the interface between a laminar and a turbulent plane Couette flow are examined by means of DNS data of a statistically steady flow field. A mixing-layer is established which neither evolves in the streamwise direction nor in time. This novel flow configuration is perfectly suited for explorations of momentum transfer mechanisms, e.g. turbulent diffusion. Unexpected undulations characterize the large-scale interactions between the turbulent and the nominally non-turbulent part flow. However, surprisingly large velocity fluctuations are observed even in the low-Re half of the flow which otherwise would be laminar.

Carbon capture and storage (CCS): the way forward

Abstract: Carbon capture and storage (CCS) is broadly recognised as having the potential to play a key role in meeting climate change targets, delivering low carbon heat and power, decarbonising industry and, more recently, its ability to facilitate the net removal of CO2 from the atmosphere. However, despite this broad consensus and its technical maturity, CCS has not yet been deployed on a scale commensurate with the ambitions articulated a decade ago. Thus, in this paper we review the current state-of-the-art of CO2 capture, transport, utilisation and storage from a multi-scale perspective, moving from the global to molecular scales. In light of the COP21 commitments to limit warming to less than 2 °C, we extend the remit of this study to include the key negative emissions technologies (NETs) of bioenergy with CCS (BECCS), and direct air capture (DAC). Cognisant of the non-technical barriers to deploying CCS, we reflect on recent experience from the UK's CCS commercialisation programme and consider the commercial and political barriers to the large-scale deployment of CCS. In all areas, we focus on identifying and clearly articulating the key research challenges that could usefully be addressed in the coming decade.

Low-Reynolds-number wakes of elliptical cylinders: from the circular cylinder to the normal flat plate

Abstract: While the wake of a circular cylinder and, to a lesser extent, the normal flat plate have been studied in considerable detail, the wakes of elliptic cylinders have not received similar attention. However, the wakes from the first two bodies have considerably different characteristics, in terms of three-dimensional transition modes, and near- and far-wake structure. This paper focuses on elliptic cylinders, which span these two disparate cases. The Strouhal number and drag coefficient variations with Reynolds number are documented for the two-dimensional shedding regime. There are considerable differences from the standard circular cylinder curve. The different three-dimensional transition modes are also examined using Floquet stability analysis based on computed two-dimensional periodic base flows. As the cylinder aspect ratio (major to minor axis) is decreased, mode A is no longer unstable for aspect ratios below 0.25, as the wake deviates further from the standard Benard–von Karman state. For still smaller aspect ratios, another three-dimensional quasi-periodic mode becomes unstable, leading to a different transition scenario. Interestingly, for the 0.25 aspect ratio case, mode A restabilises above a Reynolds number of approximately 125, allowing the wake to return to a two-dimensional state, at least in the near wake. For the flat plate, three-dimensional simulations show that the shift in the Strouhal number from the two-dimensional value is gradual with Reynolds number, unlike the situation for the circular cylinder wake once mode A shedding develops. Dynamic mode decomposition is used to characterise the spatially evolving character of the wake as it undergoes transition from the primary Benard–von Karman-like near wake into a two-layered wake, through to a secondary Benard–von Karman-like wake further downstream, which in turn develops an even longer wavelength unsteadiness. It is also used to examine the differences in the two- and three-dimensional near-wake state, showing the increasing distortion of the two-dimensional rollers as the Reynolds number is increased.

Carbon Capture and Utilization Technology without Carbon Dioxide Purification and Pressurization: A Review on Its Necessity and Available Technologies

Abstract: Carbon capture and utilization (CCU) has attracted increased attention as a means to mitigate and adapt to climate change. CCU technology regards CO2 as a raw material and reduces CO2 emissions. Ho...