Hydrocodes are widely used in the study of explosive systems but their use in routine facility vulnerability assessments has been limited due to the computational resources typically required. These ...requirements are due to the fact that the majority of hydrocodes have been developed primarily for the simulation of weapon-scale phenomena. It is not practical to use these same numerical frameworks on the large domains found in facility vulnerability studies. Here, a hydrocode formulated specifically for facility vulnerability assessments is reviewed. Techniques used to accurately represent the explosive source while maintaining computational efficiency are described. Submodels for addressing other issues found in typical terrorist attack scenarios are presented. In terrorist attack scenarios, loads produced by shocks play an important role in vulnerability. Due to the difference in the material properties of water and air and interface phenomena, there exists significant contrast in wave propagation phenomena in these two medium. These physical variations also require special attention be paid to the mathematical and numerical models used in the hydrocodes. Simulations for a variety of air and water shock scenarios are presented to validate the computational models used in the hydrocode and highlight the phenomenological issues.
Computational modeling is routinely used to design protective systems such as blast containment chambers. Hydrocodes are used to define the loads produced if the explosive items were to detonate and ...finite element analysis codes to calculate the response of the chamber. These efforts typically assume the explosive is a spherical charge. This article investigates the effect this assumption has on the blast loads and the calculated response of the chamber. First, simulations benchmarking a hydrocode with adaptive meshing and Jones–Wilkins–Lee equation of state are performed. How various aspects of the scenario affect the loading on the vessel is discussed. The code is next used to calculate the loading from a spherical charge and one representative of a configuration typically found in actual use of storage vessels. The more realistic charge configuration is found to produce higher loads on the vessel walls. The structural response of the chamber to both charge configurations is calculated using finite element analysis. The non-ideal configuration is found to produce a very different response than the typically assumed ideal spherical charge.
Explosion events from malicious activities produce tremendous losses. The magnitude of these losses is directly tied to the overpressure field generated during the event. This field is dependent on ...both the explosive charge and the environment in which the event occurs. Environmental factors, such as blast focusing and channeling, greatly alter the damage patterns. A useful tool in investigating and preparing for such events is computational fluid dynamics (CFD) modeling. Here, a CFD tool, Computational Explosion and Blast Assessment Model (CEBAM), is tested to determine the accuracy to which environmental effects can be represented. Configurations ranging from long single streets to barricaded buildings are simulated to determine the utility of CFD modeling in predicting the overpressure fields. The CEBAM simulations are found to compare well with the available test data supporting the use of CFD modeling to investigate potential events.
Evidence for a B-s(0)pi(+/-) State Askew, A.; Aushev, V.; Avila, C. ...
Physical review letters,
07/2016, Letnik:
117, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We report evidence for a narrow structure, X(5568), in the decay sequence X(5568) -> B-s(0)pi(+/-), B-s(0) -> J/psi phi, J/psi -> mu(+)mu(-), phi -> K+K-. This is evidence for the first ...instance of a hadronic state with valence quarks of four different flavors. The mass and natural width of this state are measured to be m = 5567.8 +/- 2.9(stat)(-1.9)(+0.9) (syst) MeV/c(2) and Gamma = 21.9 +/- 6.4(stat)(-2.5)(+5.0) (syst) MeV/c(2). If the decay is X(5568) -> B-s*pi(+/-). B-s(0)gamma pi(+/-) with an unseen gamma, m(X(5568)) will be shifted up by m(B-s*) - m(B-s(0)) similar to 49 MeV/c(2). This measurement is based on 10.4 fb(-1) of p (p) over bar collision data at root s = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider.
This paper presents a systems approach to determining the economic loss due to property damage resulting from a terrorist bombing in an American city. San Antonio, TX, is used as an example, but ...aspects of interest are the same as other cities (e.g. New York, Madrid, London). Existing data found in county property appraisal databases is used to produce a value map of the downtown portion of the city. A geometric representation of the city is used along with computational fluid dynamic (CFD) technology to simulate various bombing events and provide blast loadings on the various buildings. The results from the simulations are combined with damage criteria, which allows for estimations of the property damage and resulting loss. The results pinpoint locations where the loss is maximized due to a combination of the property value and the blast profiles, which are driven by the specific urban layout. Further work is suggested where principle components, such as Euclidian distance define the bulk of the causative factors.
PDF
