The Experts below are selected from a list of 84 Experts worldwide ranked by ideXlab platform
Thomas W. Shinder - One of the best experts on this subject based on the ideXlab platform.
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ISA 2006 Stateful Inspection and Application Layer Filtering
The Best Damn Firewall Book Period, 2007Co-Authors: Thomas W. ShinderAbstract:The ISA firewall is able to perform stateful application Layer Inspection, which enables it to fully inspect the communication streams passed by it from one network to another. In contrast to stateful filtering where only the network and transport Layer information is filtered, true stateful Inspection requires that the firewall be able to analyze and make decisions on all Layers of the communication, including the most important Layer, the application Layer. The Web filters perform stateful application Layer Inspection on communications handled by the ISA firewall's Web Proxy components. The Web Proxy handles connections for HTTP, HTTPS (SSL), and HTTP tunneled FTP connections. This chapter discusses the ISA firewall's application Layer filtering feature set. It discusses the two main types of application filters employed by the ISA firewall—access filters and security filters. Both the access filters and the security filters impose requirements that the connections meet specifications of legitimate communications using those protocols. Finally, the chapterdiscusses the ISA firewall's intrusion detection and prevention mechanisms. Common network Layer attacks that can be launched against the ISA firewall and how the ISA firewall protects you against them are covered in this chapter.
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Publishing Network Services with ISA 2006 Firewalls
Dr. Tom Shinder's ISA Server 2006 Migration Guide, 2007Co-Authors: Thomas W. ShinderAbstract:This chapter describes the publishing of network services with ISA 2006 Firewalls. Web Publishing and Server Publishing Rules allows one to make servers and services on ISA firewall Protected Networks available to users on both protected and nonprotected networks. One of the major advantages of using Web Publishing Rules to publish Web sites on protected networks is the ISA firewall's ability to perform very deep application-Layer Inspection on all connections made to published Web sites. Web Publishing Rules allow you to redirect connections based on the path indicated by the external user. It is found that when subsequent users make requests for the same content on the published Web server, the content is served from the ISA firewall's Web cache instead of being fetched from the Web server itself. Caching responses from published Web sites reduces the load on the published Web server and on any network segments between the ISA firewall and the published Web server. It is observed that the ISA firewall includes two wizards for publishing Mail Servers right out of the box.
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ISA 2004 Stateful Inspection and Application Layer Filtering
How to Cheat at Configuring ISA Server 2004, 2006Co-Authors: Thomas W. ShinderAbstract:The chapter discusses the ISA firewall's application Layer filtering feature set. It focuses on the two main types of application filters employed by the ISA firewall: access filters and security filters. Both access filters and security filters impose requirements that the connections meet specifications of legitimate communications using those protocols. The ISA firewall is able to perform both stateful filtering and stateful application Layer Inspection. The ISA firewall's stateful filtering feature set makes the ISA firewall a network Layer stateful firewall in the same class as any hardware firewall that performs stateful filtering at the network and transport Layers. Stateful filtering is often referred to as stateful packet Inspection. The chapter also discusses the ISA firewall's intrusion detection and prevention mechanisms.
James Buchholz - One of the best experts on this subject based on the ideXlab platform.
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The Role of Vorticity Transport in the Detachment of Unsteady Leading-Edge Vortices
54th AIAA Aerospace Sciences Meeting, 2016Co-Authors: James Akkala, James BuchholzAbstract:Multi-plane particle image velocimetry data and surface pressure measurements are used to analyze the nominally two-dimensional flow field of a high-aspect-ratio flat-plate airfoil undergoing a pure-plunge motion, as well as the three-dimensional flow field produced by a plunging flat-plate wing with aspect-ratio 2. The sources and sinks of vorticity within these flows were quantified by means of a vorticity flux analysis, the results of which verified prior conclusions that the diffusive flux of vorticity from the surface of the airfoil acts primarily as a sink of leading-edge-vortex (LEV) vorticity, with a magnitude roughly half that of the flux of vorticity introduced by the leading-edge shear Layer. Inspection of the chordwise distribution of the surface diffusive flux of vorticity within the 2D case showed it to correlate very well with the evolution of the flow field. Specifically, the diffusive flux experienced a major increase during the phase interval in which the LEV was still attached to the downstream boundary Layer, which ultimately triggered the roll-up of the LEV and generation of the secondary vortex. It was also noted that the accumulation of secondary vorticity near the leading edge prevented the diffusive flux from continuing to increase after the roll-up of the LEV. This result was validated through analysis of the 3D case, which demonstrated that maintaining an LEV that stays attached to the downstream boundary Layer produces a larger diffusive flux of vorticity–presumably consistent with an enhancement of both lift and thrust. Despite the increased diffusive flux, this state was maintained by a strong spanwise convective flux of vorticity. This observation provides a new interpretation of the role of spanwise flow on vortex evolution, and suggests a physical mechanism that may be leveraged to control the flow.
Hyung Jin Sung - One of the best experts on this subject based on the ideXlab platform.
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Direct numerical simulation of the turbulent boundary Layer over a rod-roughened wall
Journal of Fluid Mechanics, 2007Co-Authors: Seung Hyun Lee, Hyung Jin SungAbstract:The effects of surface roughness on a spatially developing turbulent boundary Layer (TBL) are investigated by performing direct numerical simulations of TBLs over rough and smooth walls. The Reynolds number based on the momentum thickness was varied in the rangeReθ = 300 ∼ 1400. The roughness elements were periodically arranged two-dimensional spanwise rods, and the roughness height was k =1 .5θin ,w hereθin is the momentum thickness at the inlet, which corresponds to k/δ =0 .045 ∼ 0.125, δ being the boundary Layer thickness. To avoid generating a rough-wall inflow, which is prohibitively difficult, a step change from smooth to rough was placed 80θin downstream from the inlet. The spatially developing characteristics of the rough-wall TBL were examined. Along the streamwise direction, the friction velocity approached a constant value, and self-preserving forms of the turbulent Reynolds stress tensors were obtained. Introduction of the roughness elements affected the turbulent stress not only in the roughness subLayer but also in the outer Layer. Despite the roughnessinduced increase of the turbulent Reynolds stress tensors in the outer Layer, the roughness had only a relatively small effect on the anisotropic Reynolds stress tensor in the outer Layer. Inspection of the triple products of the velocity fluctuations revealed that introducing the roughness elements onto the smooth wall had a marked effect on vertical turbulent transport across the whole TBL. By contrast, good surface similarity in the outer Layer was obtained for the third-order moments of the velocity fluctuations.
W. Scott Pegau - One of the best experts on this subject based on the ideXlab platform.
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Simulation of turbulent exchange processes in summertime leads
Journal of Geophysical Research, 2005Co-Authors: Eric D. Skyllingstad, Clayton A. Paulson, W. Scott PegauAbstract:[1] Ice-ocean heat exchange in polar leads was examined using a large-eddy simulation model coupled to a slab ice model. Simulations were performed using an idealized square domain for a range of lead sizes, surface wind stress (0.05–0.1 N m−2), and lead temperature/salinity profiles. Particular emphasis was placed on understanding the role of fresh water in leads and how stratification controls the heat budget and ice edge melting rate. With uniform initial conditions we found that solar heating was not strong enough to develop lead freshening via ice edge melting; even weak winds (0.02 N m−2) generated circulations that maintained a well-mixed lead. In the weak wind case, adding a fresh water flux representative of surface melt runoff provided enough additional stratification so that the lead water became isolated from the rest of the simulated ocean boundary Layer. However, stronger winds (0.1 N m−2) prevented the fresh water Layer from forming. Experiments initialized with temperature/salinity profiles similar to observed cases (fresh water Layer capping the lead) demonstrated that lateral melting rates increase with expanding lead size, agreeing with simple heat balance calculations for a square lead without vertical mixing. However, with stronger winds, lateral melting rates decreased because of greater turbulent mixing of cold water from beneath the fresh Layer. Inspection of the lead circulation indicated that the strongest melting occurred where the ice edge currents were the largest. Overall, melting fluxes for a 24 m2 lead ranged from 200 to 400 W m−2, depending on the wind speed. Without the fresh Layer, fluxes ranged from 50 to 60 W m−2, suggesting that fresh water stratification can have a dominate role in controlling ice edge melting.
James Akkala - One of the best experts on this subject based on the ideXlab platform.
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The Role of Vorticity Transport in the Detachment of Unsteady Leading-Edge Vortices
54th AIAA Aerospace Sciences Meeting, 2016Co-Authors: James Akkala, James BuchholzAbstract:Multi-plane particle image velocimetry data and surface pressure measurements are used to analyze the nominally two-dimensional flow field of a high-aspect-ratio flat-plate airfoil undergoing a pure-plunge motion, as well as the three-dimensional flow field produced by a plunging flat-plate wing with aspect-ratio 2. The sources and sinks of vorticity within these flows were quantified by means of a vorticity flux analysis, the results of which verified prior conclusions that the diffusive flux of vorticity from the surface of the airfoil acts primarily as a sink of leading-edge-vortex (LEV) vorticity, with a magnitude roughly half that of the flux of vorticity introduced by the leading-edge shear Layer. Inspection of the chordwise distribution of the surface diffusive flux of vorticity within the 2D case showed it to correlate very well with the evolution of the flow field. Specifically, the diffusive flux experienced a major increase during the phase interval in which the LEV was still attached to the downstream boundary Layer, which ultimately triggered the roll-up of the LEV and generation of the secondary vortex. It was also noted that the accumulation of secondary vorticity near the leading edge prevented the diffusive flux from continuing to increase after the roll-up of the LEV. This result was validated through analysis of the 3D case, which demonstrated that maintaining an LEV that stays attached to the downstream boundary Layer produces a larger diffusive flux of vorticity–presumably consistent with an enhancement of both lift and thrust. Despite the increased diffusive flux, this state was maintained by a strong spanwise convective flux of vorticity. This observation provides a new interpretation of the role of spanwise flow on vortex evolution, and suggests a physical mechanism that may be leveraged to control the flow.