Academic literature on the topic 'Parting plane sealing'

The production of injection-molding prototypes, e.g., molded interconnect devices (MID) prototypes, can be costly and time-consuming due to the process-specific inability to replace durable steel tooling with quicker fabricated aluminum tooling. Instead, additively manufactured soft tooling is a solution for the production of small quantities and prototypes, but producing complex parts with, e.g., undercuts, is avoided due to the necessity of additional soft tooling components. The integration of automated soft slides into soft tooling has not yet been investigated and poses a challenge for the design and endurance of the tooling. The presented study covers the design and injection-molding trial of soft tooling with integrated automated slides for the production of a complex MID prototype. The design further addresses issues like the alignment of the mold components and the sealing of the complex parting plane. The soft tooling was additively manufactured via digital light processing from a silica-filled photopolymer, and 10 proper parts were injection-molded from a laser-direct structurable glass fiber-filled PET+PBT material before the first damage on the tooling occurred. Although improvements are suggested to enhance the soft tooling durability, the designed features worked as intended and are generally transferable to other part geometries.

AbstractObjectives:This study aimed to identify the pattern of post-operative drainage following partial superficial parotidectomy with and without the use of a bipolar vessel-sealing device.Methods:Of the 49 patients undergoing parotidectomies, a bipolar vessel-sealing device was used for 20. Predictive factors included in the analysis were age, sex, body weight, operating time, tumour pathology, and diabetes mellitus, hypertension and smoking status.Results:In multivariate analyses, body weight (p = 0.026) and non-use of a bipolar vessel-sealing device (p = 0.009) were significantly associated with increased post-operative drainage after 24 hours. There was also a trend towards increased drainage in diabetic patients. Operating times were significantly shorter in the bipolar vessel-sealing device group.Conclusion:Although 24-hour drainage appears adequate for most patients, in obese and diabetic individuals there is a risk of requiring increased drainage. Therefore, the drain should be left in place for a longer period. The bipolar vessel-sealing device is safe and time-efficient, and decreases the post-operative drainage period.

Summary This paper addresses interference testing in reservoirs with conductive faults allowing fluid flow along and across the fault plane. An altered skin region around fault thrusts is also included. It is found that the classical line-source solution does not apply. When active and observation wells are located across a fault, the interference behavior resembles that of a hydraulically fractured well with bilinear flow characteristics. However, different flow regimes are developed on the pressure derivative when the well pairs are situated at the same side: initially, the basic line-source behavior; then, constant pressure effect from the fault represented by a negative unit-slope line; and, finally, bilinear flow. Interference type curves for various regions in the reservoir are developed and practical guidelines are provided for interpretation of these tests. Field data from an interference test in a faulted carbonate reservoir are analyzed and fault parameters are estimated. Introduction Faults are the most common form of heterogeneity in hydrocarbon reservoirs. The nature of fluid conductivity of faults, whether sealing or partially sealing or fully conductive, has a profound effect on oil and gas recovery from faulted reservoirs. While sealing faults block fluid and pressure communication with other regions of reservoir leading to reservoir compartmentalization, conductive faults can act as pressure support sources by allowing fluid transfer along and across their planes.1–3 Therefore, characterization of faults with respect to their conductivity behavior, fluid transmissibility potential, orientation, and geometrical attributes is important in many aspects of petroleum exploitation, field development, and production. Pressure-transient testing is a powerful tool for providing reliable and useful information about many reservoir characteristics. The use of single-well pressure-transient tests in delineating faults is abundant in the literature. The simplest of the models address estimation of distance to sealing faults.4–8 Cinco-Ley et al.9 considered an infinite conductivity fault or fracture and derived analytical solutions based on the concept of source functions. The first attempt to represent a fault as a partial barrier was introduced by Stewart10 who numerically modeled the fault zone as a vertical semipermeable barrier of negligible capacity. This model correctly imposed the linear flow pattern at the fault plane. Yaxley11 obtained analytical solutions for transient pressures by considering the fault as a semi-impermeable linear discontinuity, a generalization of the Bixel et al.12 solution for reservoirs with linear discontinuities. Ambastha et al.13 analytically modeled a partially communicating fault as a thin skin region in the reservoir. The work of Abbaszadeh and Cinco-Ley14 provided a complete generalization where a fault (or a fracture) is viewed as a separate porous medium with two-dimensional flow occurring inside the fault plane. That work showed that it was possible to estimate reservoir properties, fault conductivity, fault skin factor, and distance to the fault from a pressure-buildup or a pressure-drawdown test. Although the solutions provided by Abbaszadeh and Cinco-Ley14 are general enough to cover transient pressure distribution in a faulted reservoir, multiple-well tests of interference or pulse tests were not addressed specifically. Because the compounding experience with interference tests has demonstrated their usefulness in identifying interwell heterogeneity and other reservoir characteristics,15 their application to reservoirs with conductive faults is warranted. This paper studies interference tests when an observation well is located at either side of an infinitely long conductive fault. Various flow regimes and transient behavior occurring in such tests are discussed. Because multiple parameters are involved and the characteristics of pressure response are often complex, guidelines are provided to help in the interpretation of interference tests. Type curves specific to the right side and left side of a fault are developed and used to interpret field data from an interference test near a conductive fault. These type curves and the interpretation procedure are discussed. Assumptions and Method of Solution We consider a homogeneous isotropic reservoir of uniform thickness containing slightly compressible single-phase fluid. There is a fault of infinite extent which separates the reservoir into two regions with transmissibility and diffusivity of (?1,?1) and (?2, ?2). This situation can be created when a reservoir rock is juxtaposed against a formation with different properties. The fault plane itself has permeability kf width wf and a damaged region of permeability ka whose extent is wa as seen in Fig. 1. The active well is located at the left side of the fault, and the observation well can be situated at either side. The solution for pressure transients in this system is obtained by decoupling the reservoir and fault systems, and solving for the diffusivity equations in each system with flux distributions at the fault plane as unknowns. The flux distributions are then obtained by coupling the reservoir and fault solutions at the fault plane. The derivations are done in transformed Laplace space and the method of images along with the Green's function formulation are used. The details are given in Ref. 14. Briefly, p L D ( x D , y D , t D f ) = ∫ 0 t D f ∫ 0 ∞ u f L D ( y D ′ , τ D ) t D f − τ D { e x p [ − ( 1 − x D ) 2 + ( y D + y D ′ ) 2 4 ( t D f − τ D ) ] + e x p [ − ( 1 − x D ) 2 + ( y D − y D ′ ) 2 4 ( t D f − τ D ) ] } d y D ′ d τ D − 1 2 E i [ − x D 2 + y D 2 4 t D f ] − 1 2 E i [ − ( 2 − x D ) 2 + y D 2 4 t D f ] ( 1 ) and p R D ( x D , y D , t D f ) = M ∫ 0 t D f ∫ 0 ∞ u f R D ( y D ′ , τ D ) t D f − τ D { e x p [ − F η ( x D − 1 ) 2 + ( y D + y D ′ ) 2 4 ( t D f − τ D ) ] + e x p [ − F η ( x D − 1 ) 2 + ( y D − y D ′ ) 2 4 ( t D f − τ D ) ] } d y D ′ d τ D . ( 2 )

The water has an important role in survival of all living things on this earth. Water in underground is a natural resources and the damage that occurs can cause widespread impact and repair is quite difficult. In order to guarantee the fair used and exploitation of groundwater, a permit is required. However, in the use and exploitation of groundwater, there are people and industrial parties who did not have a permit from the government related to the prevailing laws and regulations. The purpose of this research is to find out how the regulation of underground water exploitation is carried out by the community and what are the legal consequences of unlicensed underground water exploitation. The method used in this research is normative method and analysis of legal interpretation and descriptive analysis. Data sources are primary and secondary data. The research approach used in this research is an invitation-only approach and a legal concept analysis approach. The technique of conducting legal materials is carried out by means of literature study which is legal materials are collected then processed using systematic interpretation analysis. The results of this research are first, in regulating the exploitation of groundwater, the authority and legal basis used by the government as a reference in granting permits. Second, the result of not having a permit to use ground water is the sealing of the location or place and the imposition of imprisonment in accordance with the applicable laws, namely Law Number 11 of 1974 concerning Irrigation and other regulations in accordance with the respective Regional Regulations.

Abstract Introduction The mobilization of patients with diabetic foot syndrome after surgical treatment by debridement or partial amputation is usually difficult in daily practice and in inpatient care. Aim and Method A case report – with a representative case showing the innovative possibilities of an alternative mobilization option by means of a new orthesis (“iWALK 2.0®”; IWALKFree® Inc., Mansfield, Ontario, Canada) after surgical therapy of diabetic gangrene, exemplified by the successful clinical course. Results The inpatient admission of a 59-year-old male patient revealed septic gangrene of the right foot in insulin-dependent diabetes mellitus. After admission and initial diagnosis, the calculated antibiotics therapy and initial surgical rehabilitation of the right foot took place. After stabilization and control of the infection, the minor amputation was performed at the Bona-Jäger line without primary wound closure, wound care was provided by vacuum sealing. Complicated by pre-existing peroneal paralysis of the contralateral leg following herniated disc, mobilization could be accomplished out of the wheelchair using a novel “free-hand” orthesis “iWALK 2.0” and a walker with physiotherapeutic support. Thus, while simultaneously relieving the operated foot, self-sufficient mobilization at a later time was possible. This gave the patient a positive attitude to life in addition to more independence. Conclusion The successful application of the “free-hand” site “iWALK 2.0” under the listed clinical constellation thus suggests that it is a clear alternative of “postoperative rehabilitation” in the diagnosis of a surgically treated diabetic foot gangrene after minor amputation with a consolidated wound while ultimately serving to achieve a more comprehensive level of experience for targeted use with a clearly defined indication.

Summary Two offshore, wedge-shaped reservoirs in south Louisiana were interpreted with pressure-buildup responses by comparing the results from simulated finite-element model studies. The importance of knowing the correct reservoir shape, and how it is used to interpret the generated boundary-pressure responses, is briefly discussed. Two different 3D computer models incorporating different wedge-shaped geometries simulated the test pressure-buildup response patterns. Variations in the two configurations are topologically expressed as a constant thickness and a nonconstant thickness, with smooth-surface, wedged-shaped reservoir models. The variable-thickness models are pinched-out updip at one end and faulted at the other end. Numerical well-test results demonstrated changes in the relationships between the pressure-derivative profile, the wellbore location, and the extent of partial penetration in the reservoir models. The wells were placed along the perpendicular bisector (top view) at distances starting from the apex at 5, 10, 20, 40, 50, 60, 80, and 90% of the reservoir length. Results demonstrate that boundary distance identification (such as distance, number, and type) based solely on the log-log derivative profile in rectangular and triangular wedge-shaped reservoirs should be strongly discouraged. Partial-penetration effects (PPE's) in wedge-shaped reservoirs are highly dependent on the wellbore location relative to the wedge, and the well-test-data analysis becomes more complex. Introduction The interpretation of the effect of reservoir shape on pressure-transient well-test data needs improvement. It is economically imperative to be able to generate an accurate estimate of reserves and producing potential. This is especially critical for independent operators who wish to participate in deepwater opportunities in the Gulf of Mexico. Proper interpretation of data extracted from cost-effective well tests is an integral part of describing, evaluating, and managing such reservoirs. Well-test information such as average reservoir pressure, transmissivity, pore volume, storativity, formation damage, deliverability, distance to the boundary, and completion efficiency are some of the technical inputs into economic and operational decisions. Several key economic decisions that operators have to make are:Should the reservoir be exploited?How many wells are needed to develop the reservoir?Is artificial lift necessary (and if so, when)? The identification of morphological demarcation components such as impermeable barriers (faults, intersecting faults, facies changes, erosional unconformities, and structural generated depositional pinchouts) and constant-pressure boundaries (aquifer or gas-cap) from well testing help to establish the reservoir boundaries, shape, and volume. One must remember that the geological entrapment structure or sedimentological body does not always define the reservoir's limits. Our present study provides insight into wedge-shaped reservoirs in the Gulf of Mexico. Seismic exploration can define geological shapes in either two or three dimensions in the subsurface. These shapes are expressions of the preserved structural history and depositional environments and are verified by observations of such structures in outcrops and present-day depositional environments. From a sedimentological viewpoint, the following sedimentary deposits can exhibit wedge-shaped geometries. Preserved barchan sand dunes, reworked transgressive sands, barrier-island sands, offshore bars, alluvial fan deposits, delta-front sheet sands, and lenticular channel sands form the more plausible pinchout, wedge-shaped geological models recognized in the Gulf of Mexico sedimentary sequence. Wedge-Shaped Reservoirs Reviewing the petroleum engineering literature, we found very few technical papers addressing wedge-shaped reservoir geometries and their effects on reservoir performance. Their detailed analytical results are discussed and applied to the interpretations of our model results. An overview of the conceptual models is presented as a quick orientation to emphasize some model issues. Horne and Temeng1 were the first to address the problem of recognizing, discriminating, and locating reservoir pinchouts with the Green's functions method proposed by Gringarten and Ramey2 in pressure-transient analysis. The analytical solution considered a dimensionless penetration depth of the well. Their results showed that pinchout boundaries appear similar to constant-pressure boundaries with respect to pressure-drawdown behavior and not as a perpendicular sealing boundary. Yaxley3 presented a set of simple equations for calculating the stabilized inflow performance of a well in infinite rectangular and wedge-shaped drainage systems. The basis for Yaxley's mathematical model is the application of transient linear flow (as opposed to radial flow conditions assumed for the reservoir) and the mathematical difference between a plane source and a line source in linear-flow drainage systems for various rectangular drainage shapes. The equations were derived from transient linear-flow relationships for a well located between parallel no-flow boundaries. This concept was applied to intersecting no-flow boundaries and an outer circular, no-flow, constant-pressure boundary. His approach involved a constant ßr that is interpreted as an extra pressure drop relative to a well of radius ro (radial distance to the well location), which is a result of the distortion of the radial streamline pattern. Chen and Raghavan4 developed a solution to compute pressure distributions in wedge-shaped drainage systems using Laplace transforms. Their mathematical approach overcame existing limitations in some of the previous solutions, which were mentioned earlier. By applying the inversion theorem to the Laplace transformation, they verified that the slope of the pressure profile is inversely proportional to the wedge angle of the drainage system. An examination of their results is important to the interpretation of our own simulated pressure-response issues. Generally, their model solutions showed three radial-flow periods in the absence of wellbore-storage effects. The radial-flow periods showed that:During an initial radial-flow period, neither of the impermeable boundaries registered either singly or jointly.In the second phase, one or two boundaries became evident on the pressure signature.A third radial-flow period exhibited a semi logarithmic slope proportional to p/?o, where ?o=the angle of the wedge.

Abstract Variable inlet guide vanes (VIGV) are the main control element to adjust the flow rate of industrial centrifugal compressors by customized pre-swirl in the inlet plane of the impeller. The efficient working range of VIGVs is however restricted due to open flow separation occurring at critical stagger angles. In order to overcome the narrow limitations of current blade geometries and to enhance the operating range of the compressor, split blades consisting of a separate front and tail blade segment proved to be particularly promising in previous linear-cascade measurements. Each blade segment is thereby individually staggered. This enables a gradual flow deflection along the chord length. Secondary flow losses, however, were not considered in the previous investigations with linear-cascades. To highlight the potential of the split blade concept under more application-oriented conditions including all relevant flow effects, highly resolved field measurements were conducted in the wake of annular VIGVs. Four different blade configurations, a customary reference case and three variations of the split blade with full, partial and missing sealing in the gap between the segments, were assessed using five-hole probe measurements. By investigating a wide range of stagger angles, the coverage of the full low-loss working range of the VIGV could be ensured. Especially, the fully sealed split blade configuration proved its capacity to extend the efficient operational range significantly.

AbstractCubic zirconia is a well known, highly durable material with potential uses as an actinide host phase in ceramic waste forms and inert matrix fuels and in containers for very deep borehole disposal of some highly radioactive wastes. To investigate the behaviour of this material under the conditions of possible use, a cube of ∼ 2.5 mm edge was made from a single crystal of yttriastabilized cubic zirconia doped with 0.3 wt.% CeO2. The cube was enclosed in powdered granite within a gold capsule and a small amount of H2O added before sealing. The sealed capsule was held for 4 months in a cold-seal pressure vessel at a temperature of 780°C and a pressure 150 MPa, simulating both the conditions of a deep borehole disposal involving partial melting of the host rock and the conditions under which the actinide waste form might be encapsulated in granite prior to disposal. At the end of the experiment the quenched, largely glassy, sample was cut into thin slices and studied by optical microscopy, EMPA, SEM and cathodoluminescence methods. The results show that no corrosion of the zirconia crystal or reaction with the granite melt occurred and that no detectable diffusion of elements, including Ce, in or out of the zirconia took place on the timescale of the experiment. Consequently, it appears that cubic zirconia could perform most satisfactorily as both an actinide host waste form for encapsulation in solid granite for very deep disposal and as a container material for deep borehole disposal of highly radioactive wastes (HLW), including spent fuel.

Рассмотрены аппарат уплотнения с частичной химической переработкой сырья и инновационная технология получения гранулированного активированного углеродсодержащего продукта и жидкого биотоплива методом уплотнения (пеллетирования) предварительно измельченного сырья, ускоренного гидролиза, пиролиза, с последующей активацией. Приведены результаты апробации технологии на стендовых установках и аппаратах. Показано, что по- лученные гранулы соответствуют основным показателям отечественных и за- рубежных стандартов на пеллеты из растительного сырья. В процессе произ- водства протекает химическая модификация исходного сырья, на что указывает повышенное значение содержания лигнина в образцах. При проведении пиро- лиза полученных пеллет производятся гранулированный углистый остаток, жидкое биотопливо и горючая парогазовая смесь. Из гранулированного угли- стого остатка получены активированные угли, имеющие адсорбционную активность по йоду, сравнимую с древесным углем марки ДАК. Одним из направлений дальнейших исследований является подбор различных добавок в сырье перед проведением уплотнения и грануляции для улучшения свойств пеллет, в частности повышения теплотворной способности и уменьшения зольности. Однако наиболее интересное направление использования уплотненных отходов растительной биомассы в виде пеллет – в качестве сырья для термохи- мической переработки с целью получения энергетически плотных продуктов, в частности пиролиза. Исследование показало целесообразность разработки единой автономной технологии переработки отходов растительной биомассы с по- лучением конкурентно-способных товарных продуктов: гранулированных активированных углей, жидкого биотоплива, а также парогазовой смеси с достаточной теплотворной способностью для обеспечения работы специальных топочных устройств. The paper deals with the sealing machine with partial chemical processing of raw materials and the innovative technology for obtaining granular activated carbon- containing product and liquid biofuel by the method of compaction (pelletizing) of pre-crushed raw materials, accelerated hydrolysis, pyrolysis and subsequent activation. The results of approbation of the technology on bench installations and devices are presented. It is shown that the obtained pellets correspond to the main indicators of domestic and foreign standards for pellets from vegetable raw materials. In the production process, a chemical modification of the feedstock takes place, as indicat- ed by the increased value of lignin content in the samples. When pyrolysis of the pellets is produced, a granular carbonaceous residue, liquid biofuel, and a combustible gas-vapor mixture are produced. From the granular carbonaceous residue, activated carbons with an adsorption activity of iodine comparable to charcoal of the DAK brand were obtained. One of the directions of further research is the selection of various additives into the raw material before compaction and granulation to improve the properties of pellets, in particular, to increase the calorific value and to reduce ash content. However, the most interesting direction of using compacted biomass res- idue in the form of pellets is to use as a raw material for thermochemical processing in order to obtain energetically dense products, in particular pyrolysis. The work showed the expediency of developing a single autonomous technology for plant biomass residues processing with the production of competitive commodity products: granular activated carbons, liquid biofuel, as well as steam-gas sweep with sufficient calorific value to ensure the operation of special combustion devices.

Tématem diplomové práce je revize parní turbíny Mitsubishi a výpočet utahovacích momentů šroubů dělící roviny. Tato práce je rozdělena do několika částí. Úvodní část práce obsahuje seznámení s rozsahem prováděných servisních prací na parních turbínách. Poté je zde samotná revize parní turbíny Mitsubishi. Tato revize je dělena podle jednotlivých komponent turbíny. Poté je zde stanoven seznam nutných oprav a také seznam doporučených oprav pro příští odstávku. V další části je zde shrnut výpočet utěsnění dělicích rovin a to s nebo bez odlehčení. Dále jsou rozebrány nejčastěji používané typy závitů spojovacího materiálu parních turbín. Hlavní částí práce je samotný výpočet utahovacího momentu. Výstupem této práce je poté program pro výpočet utahovacího momentu v programu Excel.

A curing press is used in the final phase of tire manufacture. A tire semi product is placed into the curing press mold and a specific pressure and temperature gives it its final shape and final mechanical properties. There are many types of curing presses; this particular press is mechanical and the pressing force is exerted by an eccentric mechanism. The size of this press allows production of tires for trucks and medium-sized tractors. The basic demands placed on this type of press include tightness of the parts which are exposed to pressure from the heating medium. This paper mainly focuses on the tightness of the vulcanizing chamber and the tightness of the mold in which the semi product of the tire is inserted. Leakage of the vulcanizing chamber may cause leakage of the heating medium which could result in injury to the machine operator. Leakage of the mold causes an overflow of rubber into the parting plane, which may result in the production of rejects. To ensure the tightness of both these components, it is necessary to create sufficient pressure between the individual components. The value of the compressive force depends on the setting of the overlap of these parts, which depends on the stiffness of the individual parts and on the force exerted from the pressure of the heating medium that acts on these parts. Finite element method (FEM) analysis of this problem was performed using Abaqus software. A computational model of the curing press was created for this numerical analysis. The geometry of the press is symmetrical and the load is centric, therefore, only half of the press was modelled. The aim of this analysis was to find the most suitable settings for the overlap of the mold (independent variable) and the overlap of the chamber (dependent variable) which ensure the smallest possible leakage of the mold and an uninterrupted contact surface between the sealing and the upper part of the chamber. The sealing of the chamber is made from rubber which was modelled for the analysis as a five term generalized Mooney-Rivlin model, also known as the James-Green-Simpson model. This model assumes hyperelastic behavior with incompressibility. The insulating plates are made of a particulate composite which was considered to be linear with isotropic properties. For strength evaluation of the composite materials, all individual components of the stress tensor were investigated according to the maximum stress criterion. Hook’s law was considered to be valid for all the metallic materials. The Von Mises criterion was used to evaluate the strength of the metallic materials. The geometry of the press was discretized using 3D linear elements with 8 nodes and with reduced integration (C3D8R). The geometry of the rubber sealing was discretized using hybrid 3D linear elements with 8 nodes and with reduced integration (C3D8RH). The overall number of elements was approximately 97,000. Calculation model enabled to compute the best overlap setting of the chamber and the mold. This setting ensures their tightness. Effect of the setting to a stress in a press was also studied and the values of the stress were in a permitted range.

Abstract Variable inlet guide vanes (VIGV) are the main control element to adjust the flow rate of industrial centrifugal compressors by customized pre-swirl in the inlet plane of the impeller. The efficient working range of VIGVs is however restricted due to open flow separation occurring at critical stagger angles. In order to overcome the narrow limitations of current blade geometries and to enhance the operating range of the compressor, split blades consisting of a separate front and tail blade segment proved to be particularly promising in previous linear-cascade measurements. Each blade segment is thereby individually staggered. This enables a gradual flow deflection along the chord length. Secondary flow losses, however, were not considered in the previous investigations with linear-cascades. To highlight the potential of the split blade concept under more application-oriented conditions including all relevant flow effects, highly resolved field measurements were conducted in the wake of annular VIGVs. Four different blade configurations, a customary reference case and three variations of the split blade with full, partial and missing sealing in the gap between the segments, were assessed using five-hole probe measurements. By investigating a wide range of stagger angles, the coverage of the full low-loss working range of the VIGV could be ensured. Especially, the fully sealed split blade configuration proved its capacity to extend the efficient operational range significantly.

Dry gas seals (DGS) are widely used in turbomachinery applications. They are recently being also recommended for sealing novel super critical CO2 turbomachinery space. However, these seals can render interesting behavior under certain operating conditions which needs to be carefully monitored so that intended level of dynamic characteristics can be achieved. The ability of these seals to maintain low leakage by riding at small clearances makes them an attractive solution where secondary flows need to be minimized. To understand the significance of some of the key design features of these seals, in this work an analysis on a gas lubricated spiral groove dry gas seal is presented. Equations in polar coordinates governing the compressible flow through the DGS gap and a numerical method to solve such non-linear partial differential equation is presented. The resulting sets of equations are solved for hydrodynamic pressure distribution and the axial separation force and the film stiffness at the rotor-stator interface is calculated. A detailed study on key spiral groove features is then performed to investigate the effect of spiral angle, groove depth, groove pitch and dam width ratio on the hydrodynamic pressure generation capacity, film stiffness and hence on overall performance of the DGS. Another important phenomenon that can occur in DGS under high operating pressure is the sonic transition. It is shown that choked flow under such conditions can take place over the dam section of the seal which manifests itself into large local pressure and temperature variations and can result into dynamic instabilities.