The main challenge facing the designers of hypersonic vehicles is the significantly high levels of pressure drag and aerodynamic heating. Although blunt noses are preferred for better heat distribution, they introduce substantial drag to the vehicle. Spikes and aerodisks proved to be efficient drag and heating reduction devices. However, for some flow conditions and model designs, the flow around spiked bodies can be unstable, which deteriorates their effectiveness. In the present study, a numerical investigation was conducted on a hemispherical body equipped with a spike of variable length and a hemispherical aerodisk of variable size in laminar hypersonic freestream conditions. A mechanism is proposed to explain the drag reduction and the cause of flow instability based on the shape of an effective body. In addition, the dependence of drag reduction on the spike's detailed design was investigated. For the models investigated in this work, an optimum aerodisk size produced the minimum drag and this optimum size was found to be inversely proportional to the spike length. Nomenclature b = arc length of half a semicircle, m C D = drag coefficient D = main body diameter, m d = aerodisk diameter, m L = spike length, m M = Mach number P = pressure, Pa q = dynamic pressure, Pa Re = Reynolds number S = surface area, m 2 s = distance along the surface, m T = temperature, K V = flow velocity, m=s = inclination of separation shock wave = specific heat ratio = efficiency of compression = inclination of the dividing streamline = dynamic viscosity, kg=m s = density, kg=m 3 Subscripts d = value inside the recirculation zone inf, 1 = freestream value o = total, stagnation value p = peak value r = reattachment value ref, = reference value

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At present IoT is immensely a descriptive term of a vision that everything should be connected to the internet. IoT applications have been widely used in several fields of social living such as healthcare and social products, industrial automation and energy. In this scenario, there are more than 14 billion interconnected digital and electronic devices in operation worldwide, the equivalent of almost two devices for every human being on earth. The IoT connects different nonliving objects through the internet and enables them to share information with their community network to automate processes for human beings and makes their lives convenient. Subsequently, objects are being amalgamated with internet connectivity and powerful data analysis capabilities that promise to change the way we work and live. The Internet is a worldwide system of interconnected computer networks that use the standard Internet protocol suite (TCP/IP) to serve billions of users globally. The most vital characteristics of IoT include connectivity, active engagement, connectivity, sensors, artificial intelligence, and small device use. This paper provides an overview of existing Internet of Things (IoT), technical details, and applications in this new emerging area as well as we are thoroughly analyzing the layer about the IoT. However, this manuscript will give a better understanding for the new researchers, who want to do research in this field of Internet of Things.

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One key feature that distinguishes the flowfield around vehicles flying in supersonic and hypersonic regimes is the bow shock wave ahead of forebody. The severe drag and aeroheating impacting these vehicles can be significantly reduced if the bow shock wave ahead of the vehicles forebodies is controlled to yield weaker system of oblique shocks. Benefits of forebody shock control include increasing flight ranges, economizing fuel consumption, reducing dead weights, and thermally protecting forebody structure and onboard equipment. Forebody shock control that has been widely studied since the early 1900s is achievable in numerous techniques that vary according to the mechanism of control. While some of these techniques have already been implemented in real systems, other techniques involve serious complications and tough trade-offs. The present paper is intended to serve as the first comprehensive survey on the field of forebody shock control devices. The objectives of the present paper are multifold. The paper categorizes the various forebody shock control devices in a physics-based manner, explains the underlying physics for each device, and surveys the key studies and state-of-the-art knowledge. The paper also addresses the existing gaps in knowledge, highlights the existing systems implementing these devices, and discusses the associated practical implementation issues and design-tradeoffs. 2. Structural devices, the mechanical spikes: 2.1. Principle of operation of mechanical spikes Drag and Aeroheating Reduction Devices Fluidic Devices Opposing jets Structural Devices Mechanical spikes Energetic Devices Energy deposition Basic devices Structural-Fluidic Devices Structural-Energetic Devices Hybrid devices