Inertial Frame Independent Forcing for Discrete Velocity Boltzmann Equation: Implications for Filtered Turbulence Simulation

We present a systematic derivation of a model based on the central moment lattice Boltzmann equation that rigorously maintains Galilean invariance of forces to simulate inertial frame independent flow fields. In this regard, the central moments, i.e. moments shifted by the local fluid velocity, of the discrete source terms of the lattice Boltzmann equation are obtained by matching those of the continuous full Boltzmann equation of various orders. This results in an exact hierarchical identity between the central moments of the source terms of a given order and the components of the central moments of the distribution functions and sources of lower orders. The corresponding source terms in velocity space are then obtained from an exact inverse transformation due to a suitable choice of orthogonal basis for moments. Furthermore, such a central moment based kinetic model is further extended by incorporating reduced compressibility effects to represent incompressible flow. Moreover, the description and simulation of fluid turbulence for full or any subset of scales or their averaged behavior should remain independent of any inertial frame of reference. Thus, based on the above formulation, a new approach in lattice Boltzmann framework to incorporate turbulence models for simulation of Galilean invariant statistical averaged or filtered turbulent fluid motion is discussed.Comment: 37 pages, 1 figur

Exploring Phenyl Embrace Interactions in Trityloxy and Tritylamino Aromatic Compounds

The area of supramolecular chemistry seeks to understand the organization of molecular structures and the interactions that hold such assemblies together by non-covalent interactions such as electrostatic, hydrogen bonding, π-π stacking interactions, and hydrophobic or solvatophobic effects. One such example that comes under supramolecular chemistry is the phenyl embrace interaction. These interactions occur due to the cooperative participation of at least three or more neighboring phenyl groups arranged as an interlocking propeller configuration to give complementary edge-to-face or offset face-to-face interactions. In order to understand the effect of functional groups on the tendencies of organic compounds to form phenyl embrace interactions, a family of trityloxy and tritylamino derivatives was synthesized and solid-state structures studied. While earlier investigations carried by Scudder and Dance focused primarily on higher incidences of six or eight-fold phenyl embrace interactions, the current work is dedicated in exploring the symmetry requirements and tendencies on the least possible phenyl embrace interactions such as four-fold and especially three-fold phenyl embrace interaction; which remained elusive so far in the field of phenyl embrace. Results from this study highlight the importance of phenyl embrace interactions. Exploring the structural features of new systems, combined with a search of the existing structures, provides a unique opportunity to probe the molecular recognition profile of this intermolecular contact involving neighboring phenyl groups

Application of NTRU Cryptographic Algorithm for securing SCADA communication

Supervisory Control and Data Acquisition (SCADA) system is a control system which is widely used in Critical Infrastructure System to monitor and control industrial processes autonomously. Most of the SCADA communication protocols are vulnerable to various types of cyber-related attacks. The currently used security standards for SCADA communication specify the use of asymmetric cryptographic algorithms like RSA or ECC for securing SCADA communications. There are certain performance issues with cryptographic solutions of these specifications when applied to SCADA system with real-time constraints and hardware limitations. To overcome this issue, in this thesis we propose the use of a faster and light-weighted NTRU cryptographic algorithm for authentication and data integrity in securing SCADA communication. Experimental research conducted on ARMv6 based Raspberry Pi and Intel Core machine shows that cryptographic operations of NTRU is two to thirty five times faster than the corresponding RSA or ECC. Usage of NTRU algorithm reduces computation and memory overhead significantly making it suitable for SCADA systems with real-time constraints and hardware limitations