Pressure Disturbances Research Articles

Strength in Numbers: The Tail End of Typhoon Songda Combines with Local Cyclones to Generate Extreme Sea Level Oscillations on the British Columbia and Washington Coasts during Mid-October 2016

Abstract From 12 to 16 October 2016, a series of three major low pressure systems, including the tail end of Typhoon Songda, crossed the coasts of British Columbia (BC) and the state of Washington (WA). Songda was generated on 2 October and, after traveling northward along the coast of Japan, turned eastward toward North America. Once there, it merged with two extratropical cyclones moving along the coast of Vancouver Island. The combined lows generated pronounced storm surges, seiches, and infragravity waves off southern BC and northern WA. Here, we examine the event in terms of sea levels measured by tide gauges and offshore bottom pressure recorders, together with reanalysis data, and high-resolution air pressure and wind measurements from 182 meteorological stations. Surge heights during the event typically exceeded 80 cm, with maximum heights of over 100 cm observed at La Push (WA) and New Westminster (BC). At Tofino, on the west coast of Vancouver Island, there was a sharp 40-cm increase in sea level on 14 October in response to a marked air pressure disturbance; slightly lower sea level peaks were also observed at other outer coast locations. In all cases, the sea level response was 1.5–2.5 times as great as that expected from the inverted barometer effect, consistent with local topographic amplification. The sea level oscillations at Tofino had the form of a forced solitary wave (“meteorological tsunami,” or meteotsunami), whereas those on the southwestern shelf off Vancouver Island are well described by classical standing-wave theory. A numerical model closely reproduces the observed meteotsunami peaks and standing-wave oscillations.

Regulasi Emosi Melalui Emotion Focus Therapy (EFT) Pada Lansia Penderita Hipertensi

The elderly have a high level of emotional sensitivity so they are easily touched by small things. It is difficult for the elderly to regulate their emotions properly when dealing with situations, especially unpleasant situations. Uncontrolled emotions cause hypertension sufferers to experience increased pulse, blood pressure and heart rhythm disturbances. This study aims to identify the effect of Emotion Focus Therapy (EFT) on emotion regulation in elderly people with hypertension. Intervention Emotion Focus Therapy (EFT) needs to be given to elderly people with hypertension to control emotions and stabilize blood pressure. The research design used was pre-experimental with one group pre-post test design. The sample in the study amounted to 30 respondents. The research results obtained before the Emotion Focus Therapy (EFT) intervention was given, most of them experienced low emotional regulation by 25 respondents (83.3%) and hypertension level 1 by 22 respondents (73.3%). After receiving the EFT intervention, there was an increase in emotional control. It was found that 23 respondents (76.67%) experienced moderate emotional regulation and 18 respondents (60%) had pre-hypertension. Analysis using Wilcoxon signed rank test. The statistical test results showed a p value = 0.000 (α≤0.05) so it could be concluded that the EFT intervention had an effect on the emotional regulation of hypertension sufferers at the elderly Posyandu RW 13 Platuk Donomulyo, Sidotopo Wetan Village, Kenjeran District, Surabaya. EFT is very effective as an effort to manage emotions in elderly people with hypertension by changing awareness, response, expression, reflection and transformation of emotions. Researchers recommend EFT as an emotional regulation intervention for elderly people with hypertension.

Tsunami waves induced by the atmospheric pressure disturbance originating from the 2022 volcanic eruption in Tonga

On January 15, 2022, a violent eruption of Tonga volcano formed an explosion-like atmospheric shock wave, and subsequently many parts of the Pacific coast were hit by tsunami waves. This study focuses on the leading tsunami wave tightly linked with the widespread atmospheric pressure disturbance, and attempts to reveal whether the notable tsunami waves along the coast of Japan are attribute to the mechanism of Proudman resonance. It can be clearly shown that a pressure disturbance radiating from the volcanic eruption spread rapidly over the Pacific Ocean with an average speed of 309 m/s, while a group of tsunami waves appeared closely following the atmospheric disturbance. In most area of the Pacific Basin, the pressure disturbance moved too fast to excite the Proudman resonance, which is proved by the DART data in the deep ocean. The leading tsunami wave associating with the pressure disturbance was several centimeters high in deep ocean, but could be more than 20 cm along the coast of Japan. Based on the analysis of observation data and numerical simulation, it is revealed that the nearshore amplification instead of the Proudman resonance plays the dominant role in producing the threatening nearshore tsunamis, which may not be easily detected and aware by deep water buoys.

A Gain Scheduling Design Method of the Aero-Engine Fuel Servo Constant Pressure Valve with High Accuracy and Fast Response Ability

Constant pressure valve, which has an axially symmetric structure, is an essential component to supply the servo reference pressure for aero-engine hydraulic mechanical control systems, and its performance directly impacts the performance of the control system. This paper constructs a closed-loop disturbance rejection system of the constant pressure valve based on the linear incremental description method, in which the controlled object is the controlled pressure, and the stabilization controller is constructed by the closed-loop feedback motion valve. Meanwhile, the linear models of the closed-loop system are calculated. Subsequently, based on the bode frequency domain characteristic analysis, the accurate influences of the stabilization control gain on the dynamic performance and stability of the system are given. On this basis, a gain scheduling design method of the system is proposed, and the geometry design and implementation method of the inlet orifice is proposed to complete the design work. The simulation results show that under bad conditions, which include the 1 MPa strong step disturbance of the inlet pressure and the step disturbance of the variable outlet flow area, the steady-state working range of the controlled pressure is 1.5 ± 0.01 MPa, the steady-state error is not more than 0.7%, and the regulation time is not more than 0.006 s.

Ocean-Wave Gradiometry: Visualizing and Extracting Propagation Features of the 15 January 2022 Tsunami Wavefield with Dense Ocean-Bottom Pressure Gauge Arrays

Abstract Dense geophysical observation networks have recently enabled monitoring the wavefield of sea-bottom pressure changes. Significant sea-bottom pressure disturbances were recorded by ocean-bottom pressure gauge (OBPG) arrays around Japan on 15 January 2022, the day of the massive eruption of Hunga Tonga–Hunga Ha’apai volcano in the Tonga Islands. At the same time, sea-surface height disturbances and atmospheric pressure disturbances were recorded by tide gauges around the Pacific Ocean and barometers around the world. Because the atmospheric disturbances may have affected the propagation of the sea-surface height changes, we investigated the propagation properties of the sea-bottom pressure disturbances recorded by the OBPG arrays around Japan using wave gradiometry. We found that the leading pressure disturbances propagated from southeast to northwest with a velocity expected from linear long-wave theory for ocean waves, that is, tsunamis. We also detected several later coherent sea-bottom pressure disturbances that propagated at the velocity of tsunamis. In addition, we detected anomalous short-period later phases of pressure disturbances with propagation directions more nearly north–south than those of the leading disturbances at the coast of southwestern Japan. These results indicate that the pressure disturbances recorded at the OBPG arrays propagated as tsunamis rather than sea-surface disturbances excited by atmospheric Lamb waves, although atmospheric pressure disturbances might have affected the amplitude of sea-surface height changes. This study demonstrates that wave gradiometry can be successfully applied to data from a dense OBPG array and may be suitable for real-time monitoring of sea-bottom pressure wavefields.

Global propagation of air pressure waves and consequent ocean waves due to the January 2022 Hunga Tonga-Hunga Ha'apai eruption

On January 15, 2022, the Hunga Tonga-Hunga Ha'apai volcano's huge eruption generated tsunami waves globally due to an unusual source in this unique event: fast-traveling air pressure disturbances originated from the explosion of the volcano. Here we investigate the global propagation of the pressure waves (first cycle) and the consequent ocean waves. The analysis of the measured air pressure waves shows that the speed of air pressure linearly increases with time. The peak and trough amplitudes of the pressure wave exponentially decrease with the traveled distance until half the overall distance; then, it restarts to increase, reaching a peak towards the apogee. Two different modeling approaches are followed to solve the air pressure waves and the resulting ocean waves: i) a synthetic pressure forcing model based on barometric measurements and ii) a numerical model based on nonlinear shallow water theory using an initial disturbance at the volcano. We forced the hydrodynamic model by the produced pressure fields to compute the resulting tsunami waves globally. We present the modeling results, discussing the possible sea level amplification mechanisms and affecting factors. Fairly well agreement between the computed and measured air pressure waves and sea levels around the globe is promising.

Frequency Domain Design Method of the Aeroengine Fuel Servo Constant Pressure Difference Control System with High Performance

The constant pressure difference regulating mechanism is widely used in aeroengine fuel servo metering systems, and it almost decides the metering precision. However, the design theory and design method of the available constant pressure difference regulating mechanism are unclear, and it is difficult to follow the high stability, high accuracy, and high robustness requirements of the modern aeroengine fuel servo metering system. In this paper, the design theory of the constant pressure difference regulating mechanism is revealed, and it indicates that it consists of two basic control units: a state feedback stabilization controller to ensure the asymptotic stability and disturbance rejection performance; and a servo and feed-forward compensator to ensure the asymptotic tracking ability. In addition, based on the frequency domain analysis method, the decisive influences about the control gains of the two control units on the dynamic performance and stability are analyzed. On this basis, a frequency domain design method of the two core control gains is proposed to complete the design task of the closed-loop system. The simulation results show that, under the adverse conditions of 1 MPa strong step disturbance of the inlet pressure and 50 mm2 strong step disturbance of the variable inlet flow area, the steady-state working range of the controlled pressure difference meets 0.92 ± 0.01 MPa, the steady-state error is not more than 1%, the regulation time is not more than 0.01 s, the dynamic overshoot is not more than 10%, and the designed phase margin is more than 70°.

Mitigating Forced Shock-Wave Oscillation with Two-Dimensional Wavy Surface

Oscillating flow is one challenge for wide-Mach-number-range flight with supersonic/hype-rsonic vehicles. Aiming to mitigate the large-amplitude forced shock-wave oscillation, a 2D wavy surface has been implemented onto the flat-bottomed wall of the Sajben diffuser under downstream pressure disturbance. The oscillating SBLI in the diffuser is captured using the finite volume method with the second-order implicit dual-time-stepping method. Impacts of the wavy surface on the forced shock-wave oscillation are numerically investigated. It is found that increasing the wavy surface’s depth benefits mitigation of the shock-wave oscillation amplitudes on the walls under the given conditions, but that decreasing the wavy surface’s length may increase or decrease the oscillation amplitudes, depending on the specific value. The mitigating mechanism is interpreted from two viewpoints, i.e., the shock-wave stability and the work performed by a moving shock-wave. The transient second shock-wave temporally appears in the flow field and can be explained by the post-shock expansion.

Disturbance Observer-Based Sliding Mode Controller for Underwater Electro-Hydrostatic Actuator Affected by Seawater Pressure

This paper presents a disturbance-observer-based sliding mode control strategy for an underwater electro-hydrostatic actuator, particularly considering that electro-hydrostatic actuators (EHAs) significantly suffer from sea pressure disturbance, which makes it hard to achieve high-precision position control. Therefore, a nonlinear disturbance observer was designed to aim at the matched and mismatched disturbance caused by sea pressure disturbance. Then, a nonlinearities model for an underwater EHA was established, and a related non-singular fast terminal sliding mode (NFTSM) controller was designed by changing the conventional sliding mode surface to further improve the control accuracy. In addition, the backstepping tool was used to guarantee the robust stability of the entire three-order hydraulic dynamic system. Finally, a comparative simulation was conducted with different load forces in AMESim and Simulink, which effectively verified the high tracking performance of the proposed control strategy.

Observation of Rayleigh-Lamb waves generated by the 2022 Hunga-Tonga volcanic eruption with the POLA detectors at Ny-Ålesund

The eruption of the Hunga-Tonga volcano in the South Pacific Ocean on January 15, 2022, at about 4:15 UTC, generated a violent explosion, which created atmospheric pressure disturbances in the form of Rayleigh-Lamb waves detected all over the globe. Here we discuss the observation of the Hunga-Tonga shock-wave performed at the Ny-Ålesund Research Station on the Spitsbergen island, by the detectors of the PolarquEEEst experiment and their ancillary sensors. Online pressure data as well as the results of dedicated offline analysis are presented and discussed in details. Results include wave arrival times, wave amplitude measurements and wave velocity calculation. We observed five passages of the shock wave with a significance larger than 3 sigma and an amplitude up to 1 hPa. The average propagation velocity resulted to be (308 ± 0.6) m/s. Possible effects of the atmospheric pressure variation associated with the shock-wave multiple passages on the cosmic-ray rate at ground level are also investigated. We did not find any significant evidence of this effect.

Influence of inlet pressure disturbance on transient performance of liquid oxygen lubricated mechanical seal and rub-impact phenomenon caused by excitation overload

The dynamic stability of the non-contacting mechanical seal (NMS) under variable working conditions is a vital factor for the reliable operation of rotating equipment. This paper presents a transient dynamic model to investigate the parametric response of liquid oxygen lubricated NMS under inlet pressure disturbance, which comprehensively considers asperity contact, micro-clearance lubrication and dynamic motion of a flexible mounted ring. Meanwhile, various forms of rub-impact phenomenon and dynamic instability caused by excitation overload are also analyzed. Lastly, an experimental research is proposed with diverse sensors to monitor the parameter data under pressure disturbance. In addition, the characteristics of acoustic emission signals when rub-impact of friction pair occurs are further investigated and processed, including various impact forms and location method.

Water waves generated by moving atmospheric pressure: theoretical analyses with applications to the 2022 Tonga event

Both one-dimensional in the horizontal direction (1DH, dispersive and non-dispersive) and two-dimensional in the horizontal direction (2DH) axisymmetric (approximate, non-dispersive) analytical solutions are derived for water waves generated by moving atmospheric pressures. For 1DH, three wave components can be identified: the locked wave propagating with the speed of the atmospheric pressure, $C_p$ , and two free wave components propagating in opposite directions with the respective wave celerity, according to the linear frequency dispersion relationship. Under the supercritical condition ( $C_p > C$ , which is the fastest celerity of the water wave), the leading water wave is the locked wave and has the same sign (i.e. phase) as the atmospheric pressure, while the trailing free wave has the opposite sign. Under the subcritical condition ( $C >C_p$ ) the fastest moving free wave component leads, and its free surface elevation has the same sign as the atmospheric pressure. For a long atmospheric pressure disturbance, the induced free surface profile mimics that of the atmospheric pressure. The 2DH problem involves an axisymmetric atmospheric pressure decaying in the radial direction as $O(r^{-1/2})$ . Due to symmetry, only two wave components, locked and free, appear. The tsunami DART data captured during Tonga's volcanic eruption event are analysed. Corrections are necessary to isolate the free surface elevation data. Comparisons between the corrected DART data and the analytical solutions, including the arrival times of the leading locked waves and the trailing free waves, and the amplitude ratios, are in agreement in order of magnitude.

Oil Cavitation Morphology Analysis of Textured Cylindrical Rotating Friction Pair on Circular-Disk End Faces

Cavitation is a destructive hydraulic phenomenon; it causes damage to small hydraulic machinery and large water-conservancy projects, and cavitation and cavitation corrosion problems are long-standing problems for hydraulic machinery experts. Micro-textures are often machined onto the end face near the indirect contact point to increase the oil film bearing capacity and reduce the transfer torque in hydraulic machinery, but the pressure disturbance caused by the texture dimple and boundary can induce cavitation. To delay or eliminate cavitation on the textured surface of equipment such as mechanical seals and dynamic bearings, the cavitation effect of a cylindrical texture on a rotating frictional pair was investigated from theoretical, imitational, and experimental perspectives. Low pressure is extremely important for inducing cavitation; once cavitation conditions are met, a full bubble can be formed in about 0.015 s. Cavitation mainly occurs at the outer radius of the rotating end face, i.e., in the high-speed region. There is a mutual mass transfer between gas and liquid phases when cavitation occurs, but the generation of cavitation bubbles is faster than its collapse, thus causing an increasing cavitation region.

Annular Dump Diffuser and Deswirl System for Back-Pressure Control in Engine-Scale Transonic Annular Cascade

Abstract A common requirement for turbomachinery testing facilities is the ability to independently control Mach number and Reynolds number. In practice, this means independent control of the inlet total pressure and exit static pressure in a test facility. In this paper, we present a solution to this problem with particular applicability to large-scale annular test facilities. We describe the design and commissioning of a combined annular dump diffuser and deswirl system for back-pressure control in environments with high-whirl transonic flow. The particular application was an annular cascade of nozzle guide vanes from a current civil engine. The purpose was to provide independent control of Mach number and Reynolds number, by controlling the back-pressure in the intermediate annular plenum which forms the dump diffuser. The dump diffuser is necessary to facilitate optical and probe access (without interaction effects) and to reduce the risk of exit static pressure disturbances (due to particular duct design). The system has been installed and validated in the engine component aerothermal (ECAT) facility at the University of Oxford. In this implementation of the system, the high-whirl transonic flow from the nozzle guide vanes passes through a short, parallel annular duct, and is dumped into an annular plenum, before being re-accelerated into a deswirl vane ring. The deswirl ring turns the flow to the axial direction. The flow is then discharged through a variable choke plate into a silencer. Conditioning the flow to have zero whirl at the choke plate reduces the sensitivity of the choke plate effective blockage to the whirl angle. The design, deswirl vane aerodynamic performance, and overall system performance are assessed with detailed experiments and 3D unsteady computational fluid dynamics predictions. The control of high-whirl transonic flow is notoriously challenging, and the deswirl system has application to exhaust conditioning in a number of applications including annular cascade experiments and rocket turbo-pump exhaust systems.

PENENTUAN SENSITIVITAS YANG BERPENGARUH TERHADAP PRODUKSI RESERVOIR MULTILAYER SECARA COMMINGLE

Multilayer reservoirs are not uncommon in oil and gas fields. In optimizing production in multilayer reservoirs, commingle production is an option. When producing a multilayer reservoir, it is necessary to select a reservoir with suitable characteristics. More and more research in producing multilayer reservoirs by commingle is being carried out. Forchheimer conducted research on the effect of turbulence that occurs, especially in gas wells. This turbulence effect causes pressure disturbances from the reservoir into the well. When the reservoir is produced in commingle, how does gas turbulence affect the production. This research is devoted to the production of commingle wells that penetrate three layers of a multilayer dry gas reservoir by considering the turbulence that occurs. Then it is determined the possible sensitivity that has an effect using literature studies in the multilayer field and gas well field based on the cumulative changes in production that occur in each sensitivity.

Disturbance indicator values for European plants

AbstractMotivationIndicator values are numerical values used to characterize the ecological niches of species and to estimate their occurrence along gradients. Indicator values on climatic and edaphic niches of plant species have received considerable attention in ecological research, whereas data on the optimal positioning of species along disturbance gradients are less developed. Here, we present a new data set of disturbance indicator values identifying optima along gradients of natural and anthropogenic disturbance for 6382 vascular plant species based on the analysis of 736,366 European vegetation plots and using expert‐based characterization of disturbance regimes in 236 habitat types. The indicator values presented here are crucial for integrating disturbance niche optima into large‐scale vegetation analyses and macroecological studies.Main types of variables containedWe set up five main continuous indicator values for European vascular plants: disturbance severity, disturbance frequency, mowing frequency, grazing pressure and soil disturbance. The first two indicators are provided separately for the whole community and for the herb layer. We calculated the values as the average of expert‐based estimates of disturbance values in all habitat types where a species occurs, weighted by the number of plots in which the species occurs within a given habitat type.Spatial location and grainEurope. Vegetation plots ranging in size from 1 to 1000 m2.Time period and grainVegetation plots mostly sampled between 1956 and 2013 (= 5th and 95th quantiles of the sampling year, respectively).Major taxa and level of measurementSpecies‐level indicator values for vascular plants.Software formatcsv file.

Closed-type pneumatic temperature control of a pressure-controlled loop heat pipe with a mechanically driven gas pressure controller

Precise and rapid temperature controls without overshooting or undershooting are of prime importance in numerous industrial and scientific applications. The recently-suggested pneumatic temperature control technique with a pressure-controlled loop heat pipe (PCLHP) was considered to be a fit-for-purpose method achieving those required features despite its open nature caused by use of an open-type commercial gas pressure controller. In this work, a closed-type pneumatic temperature control method was established based on the PCLHP equipped with a mechanically driven gas pressure controller (MDGPC). The MDGPC comprised a variable-volume bellows chamber and a linear actuator, and gas pressure control was realized by varying the axial dimension of the bellows chamber. The MDGPC attained a pressure control stability and resolution of approximately 1 Pa and 10 Pa, respectively. Rapid and stable recovery from sudden external pressure disturbances was demonstrated, and stepwise pressure changes of ±5 kPa were successfully achieved with a stability of approximately 1 Pa without any instabilities. With the MDGPC, pneumatic temperature control of the PCLHP was realized in a closed manner; the stability of the pneumatically controlled temperature was approximately 0.01 °C, which is comparable to the stability obtained with a commercial open-type gas pressure controller. Temperature steps of approximately 0.8 °C were generated via pressure steps of ±2.5 kPa, and the change in temperature was accurately predicted with a thermodynamic relationship. Wide-range and stable temperature changes were also attained under gradual pressure changes generated by the MDGPC. Overall, closed-type pneumatic temperature control of the PCLHP was successfully realized with the MDGPC.

Wellbore Temperature and Pressure Calculation of Offshore Gas Well Based on Gas–Liquid Separated Flow Model

Compared with land wells, the production environment and reservoir depth of offshore oil and gas wells are more complex and shallower. Further, HPHT production fluid there will produce strong temperature and pressure disturbance that affects the wellbore, which easily generates wellbore safety problems, such as wellhead growth and leakage caused by the incompatible deformation of casing and cement sheath. Therefore, obtaining an accurate wellbore temperature and pressure field is the key to implementing a wellbore safety assessment. Based on the gas–liquid two-phase separated method, this paper established an improved calculation model of wellbore temperature and pressure field for offshore HPHT wells. This model also takes into account the heat transfer environment characteristics of “formation-seawater-air” and the influence of well structure. Compared with the measured data of the case well, the error of temperature and pressure calculation results of the improved model are only 0.87% and 2.46%. Further, its calculation accuracy is greatly improved compared to that of the traditional gas–liquid homogeneous flow calculation model. Based on this model, the influencing factors of wellbore temperature and pressure in offshore gas wells are analyzed. The results show that forced convection heat exchange between seawater–air and wellbore is stronger than that between wellbore and formation. Reducing the gas–liquid ratio of the product can effectively reduce wellbore temperature and increase wellbore pressure. The gas production has a significant impact on the wellbore temperature. When the gas production rises from 10 × 104⋅m3/d to 60 × 104⋅m3/d, the wellhead temperature rises from 63 °C to 99 °C. However, due to the mutual influence of friction pressure drop and hydrostatic pressure drop, wellbore pressure increases first and then decreases with the increase in gas production. The improved model can provide a more accurate estimate of the time to reach the rated wellhead temperature. Meanwhile, this model displays accurate theoretical support for the rational formulation of the production plan after the well opening, so as to avoid excessive restrictions on the initial production rate.

Cavitation Morphology Study between Hemispherical Textured Rotating Friction Pairs

A non-direct contact rotary interface uses a viscous fluid as the lubricant working medium. Because the oil film friction coefficient formed is extremely small, so it has great application potential in sealing, fluid transmission, thermosolutal convection, and bionics. Research on mechanical seals, wet clutches, and dynamic load bearing have proven that micro-textures can effectively improve friction and lubrication performance. However, when the fluid flows through the texture boundary, pressure disturbances can induce hydrodynamic cavitation. A pair of rotating disks are selected as our research objects. From the simulation and experiment research, we found that cavitation volume does not always increase with an increase in the texture rate, and cavitation always occurs preferentially at the outer diameter, so it is necessary to avoid machining the texture structure at the outer diameter of the mechanical seal end. Once the conditions for cavitation are met, a complete cavity is formed in approximately 0.015 s. The study also verifies that the cavitation gas originates from the phase change of the oil.

Mechanism and characteristics of thrust generated by a submerged detonation tube for underwater propulsion

The detonation engine, which can produce high specific impulse during the underwater detonation process (UDP), has become the forefront of underwater propulsion. In this paper, the thrust mechanism conducted in UDP and the propagation characteristics of the complex pressure waves are numerically studied, and the correlation between those two features is analyzed. The thrust from UDP is generated in a submerged detonation tube (SDT) and driven by the stoichiometric methane-oxygen mixture. The results show that detonation of the pre-filled combustible gas mixture gives rise to complex pressure waves and delivers several force impulses to the SDT. The impulses present different effects on the thrust performance, which is divided into two stages. In the first stage, before the detonation wave collides with the exterior water, the thrust is provided by the persistent back pressure effect of the detonation product. When the detonation wave propagates through the SDT exit and strikes the gas–water interface, a transmitted shock wave and a reflected shock wave are formed, which produce the impulses dominating the second stage. The reflected shock wave eventually impinges on the inner wall, imposing a force impulse on it. The pressure disturbance on the annular wall caused by the transmitted shock wave and subsequent detonation gas jet leads to another two thrust impulses. Finally, a comparison between the thrust of the SDT and its counterpart in the air is conducted to characterize the influence of UDP, and the effects of dimensional parameters of the SDT are also investigated.