Equipment for Damping Hydraulic Shocks in Pressure Hydrotransport Facilities

Newly developed equipment for damping hydraulic shocks in pressure hydrotransport facilities is reviewed in this article. This equipment includes a discharge, safety diaphragm, as well as a flexible diaphragm, which is connected to the main pipeline at both different ends of the backpressure valve. A rupture disc is attached to it from below and load is attached from above by means of a rod, so that it can efficiently act during movement of hydraulic fluid in the central main pipeline, i.e. when the flow to be transported contains abrasive contaminant of solid material. The load represents a piston, which is rigidly connected to the flexible diaphragm and the rupture disc and creates an airproof space filled with viscous fluid. At the same time, the lower space is isolated from the main pipeline by a flexible separating element before the backpressure valve and the upper space is also isolated by a flexible separating element located after the back pressure valve.

SEIMSIC CONDITION ASSESSMENT OF TEMPLE A CASE STUDY ON SHIVA-PARBATI TEMPLE

Shiva Parvati temple is an uncommon shrine built on a four-step brick platform. It stands out particularly due to its three golden pinnacles. It was Bahadur Shah Idea to construct a hybrid temple that incorporated Newar and Rajput style on top of the pavilion built by King Laxmi Narasimha Malla who ruled in the seventeenth century. The temple has been renovated in 1998AD. The golden pinnacle of this temple is quite artistic and one of the best in the Durbar Square. It consists of three tapering spires alternating with four floral stalks on a small platform. It is unique because it departs from the traditional Newar appearance and adopts the Rajput/Mughal style. Shiva-Parvati Temple which is adorned with images of Shiva and his consort Parvati. With its “Shiva-Parvati Temple” historical importance as Monument underlying the UNESCO World Heritage Sites and One which is affected by the Gorkha Earthquake (2015). The main objective of the study is to carry out seismic condition assessment of the temple based on detail damage assessment. A set of Architectural and Structural Drawings has been prepared along with the NonDestructive Tests and Finite Element Modeling by using the Structural Analysis and Design software SAP. The temple is built with the traditional newer construction technology with load bearing walls in surkhi mortar cladding on outer face by Dachi Appa and floor and roof with timber members. This paper focuses on the visual damage assessment and detail study of the cracks in different locations of the temple. The flexible diaphragm, lack of bands and insufficient chukuls (Spikes) leads to the damage on the Temple.

Dynamic Characteristics of a Segmented Supercritical Driveline with Flexible Couplings and Dry Friction Dampers

Helicopter tail rotors adopt a segmented driveline connected by flexible couplings, and dry friction dampers to suppress resonance. Modeling for this system can provide a basic foundation for parameter analysis. In this work, the lateral-torsional vibration equation of the shaft with continuous internal damping is established. The static and dynamic effects caused by flexible diaphragm couplings subject to parallel and angular misalignment is derived. A novel dual rub-impact model between the shaft and dry friction damper with multiple stages is proposed. Finally, a model of a helicopter tail rotor driveline incorporating all the above elements is formulated. Numerical simulations are carried out by an improved Adams–Bashforth method following the design flowchart. The dynamics of multiple vibration suppression, and the static and dynamic misalignment are analyzed to illustrate the accuracy and characteristics of the model. The coeffect of the rub impact and the misalignment on shafts and dampers are presented through the results of simulation and experiment. It provides an accurate and comprehensive mathematical model for the helicopter driveline. Response characteristics of multiple damping stages, static and dynamic misalignment, and their interaction are revealed.

Synthetic jet for underwater flow control applications

The formation, propagation, and interaction of vortex rings have been the subject of various researchers due to its wide application in nature and day-to-day life. Some of the important applications of vortex rings are volcanic eruption, propulsion of aquatic creatures, sewerage outfalls. As an active device, synthetic jet with a train of large scale coherent structures and zero net mass flow have many practical and industrial applications in flow control.A synthetic jet is generated using a simple cavity with a small orifice at one end and a deformable flexible diaphragm at the opposite end oscillating at different frequency and amplitude. It generates a series of vortex rings due to the changes in the cavity size with diaphragm oscillation. The vortex ring moves away from the orifice exit plane under the influence of self-induced velocity and thus synthesize a jet. Synthetic jet is also called zero net mass flux (ZNMF) system, the net mass transfer through the opening in one cycle is zero but the jet imparts a net transport of momentum to the surroundings.In this work, the aim is to study the characteristics of synthetic jet for various orifice shapes, actuation frequencies and diaphragm displacements. A series of experiments were performed to understand the behavior of circular and rectangular shape synthetic jet in quiescent flow environment. To achieve this, a synthetic jet generation unit mounted on the sidewall of water tank is used. Further, a torpedo shape model with built-in circularsynthetic jet has been designed and developed and the behavior of synthetic jet in crossflow has been investigated. For qualitative study, the bulk flow visualization and laser induced fluorescence (LIF) technique has been used whereas for quantitative measurement, the velocity is measured using hot-film anemometry and Laser Doppler Velocimetry (LDV). Circular orifices of 8, 10 and 13 mm diameter operating at actuation frequencies of 1, 2, 4 and 6 Hz have been used for characterization of circular synthetic jet generation.

Failures of Flexible Diaphragm Couplings of Power Take Off (PTO) Shafts of an Aircraft by Surface Discontinuity, Controlled by Stress Concentration or Stress Intensity Factor

Failures of two power take off (PTO) shafts of an aircraft have been analysed. Two shafts, one each developed by two different manufacturers failed separately during power run endurance test conducted at room temperature and ambient normal atmosphere. In both the cases, cracks were observed on the outer diaphragm disc. One shaft showed cracking in the engine side, while the other one exhibited cracks in the aircraft mounting accessory gearbox (AMAGB) side. Chemical analysis, microstructure and hardness evaluation indicate that the diaphragm material of the shafts is Ti-6Al-4V alloy used in solution treated and aged condition, as per the desired specification AMS 4928. Microstructural in-homogeneity, possibly a result of improper forging, was observed in diaphragm material of both the shafts. Additionally, surface discontinuities induced by forging and subsequent insufficient machining were noticed on the diaphragms. The diaphragms failed by fatigue with cracks possibly nucleating at surface discontinuities. Discontinuities with lower availability in one shaft led to somewhat increased life (466 million cycles) as compared to the life (104 million cycles) of the other shaft. Another possible factor contributing to lower life in the later shaft is the presence of higher quantity of nitrogen rich inclusions. Controlling factor triggering the failure of diaphragm of shaft with lower life seems to be the available high stress level along the rim periphery, while that for shaft with higher life is presence of few localized sharp surface discontinuities.

Evaluating second-order effects in rigid wall-flexible roof diaphragm buildings

When evaluating seismically induced second-order effects in buildings, engineers and researchers are most familiar with these concerns in the context of multistory buildings with rigid diaphragms. However, similar concerns are valid for short single-story concrete or masonry-walled buildings with larger flexible diaphragms, which is a significant portion of the building stock in the United States. These rigid wall-flexible diaphragm (RWFD) buildings may have significant diaphragm drifts causing induced second-order effects. The stability coefficient currently found in ASCE 7 has traditionally been used by practitioners to evaluate the relative risk of P-delta instability in multistory buildings, but this indicator can be adapted for use in RWFD buildings. Using numerical studies following the Federal Emergency Management Agency (FEMA) P-695 collapse assessment methodology to evaluate the risk of collapse for a set of RWFD archetype buildings, a modified stability coefficient for RWFD buildings is found to capture the trend toward P-delta collapse and can act as a reasonable indicator without the need for heavy computational efforts.

Characterization of Impingement Heat/Mass Transfer to the Synthetic Jet Generated by a Biomimetic Actuator

Two biomimetic synthetic jet (SJ) actuators were designed, manufactured, and tested under conditions of a jet impingement onto a wall. Nozzles of the actuators were formed by a flexible diaphragm rim, the working fluid was air, and the operating frequencies were chosen near the resonance at 65 Hz and 69 Hz. Four experimental methods were used: phase-locked visualization of the oscillating nozzle lips, jet momentum flux measurement using a precision scale, hot-wire anemometry, and mass transfer measurement using the naphthalene sublimation technique. The results demonstrated possibilities of the proposed actuators to cause a desired heat/mass transfer distribution on the exposed wall. It was concluded that the heat/mass transfer rate was commensurable with a conventional continuous impinging jets (IJs) at the same Reynolds numbers.

A Synthetic Jet Issuing From a Bio-Inspired Actuator With an Oscillating Nozzle Lip

A novel variant of a synthetic jet actuator (SJA) has been designed, manufactured, and tested. The novelty consists in a bio-inspired nozzle whose oscillating lip is formed by a flexible diaphragm rim. The working fluid is air, and the operating frequency is 65 Hz. The proposed SJA was tested by three experimental methods: phase-locked visualization of the nozzle lips, hot-wire anemometry, and momentum flux measurement using a precision scale. The results demonstrate advantages of the proposed SJA, namely, an increase in the momentum flux by 18% compared with that of a conventional SJA.