1,721,033 research outputs found
Pipeline Systems
No full textPipeline circuits are the most common application of Hydraulics and Fluid Mechanics in civil and industrial engineering. The liquid is conveyed into pipes of various diameters and roughness, usually in the presence of special components such as valves, curves, elbows, fittings. In most cases the problems can be solved by applying the energy balance in terms of Bernoulli’s extended theorem with additional energy losses. Energy losses belong to the category of concentrated and distributed losses, both proportional to the velocity head (at least in turbulent conditions) with a coefficient that depends on the type of the special component, on the roughness of the duct and on the Reynolds number. In particular, the distributed energy losses are calculated with the Darcy formula where the friction factor is calculated with the Moody chart or, in case of turbulent flow, with the Colebrook–White equation, an equation in implicit form of the friction factor, the relative roughness and the number of Reynolds The Colebrook–White equation in the general case has no analytical solution, and a numerical procedure is required, if necessary with iterations
Trend di precipitazione e temperature: confronti fra informazione storica e modelli climatici di previsione
No full textLa memoria analizza i trend temporali delle precipitazioni e delle temperature, storicamente osservate, e le future proiezioni climatiche con riferimento alla parte set-tentrionale della Toscana. I trend sono identificati e quantificati a scala mensile e an-nuale presso stazioni di misura con a disposizione lunghe serie storiche di dati (60-90 anni). Sono stati poi considerati 13 modelli climatici regionali (RCM), basati su due scenari di emissione di gas serra (RCP4.5 e RCP8.5), allo scopo di ottenere le proiezioni di precipitazione e temperatura del futuro e rappresentare l'incertezza dei risultati. I dati storici evidenziano, globalmente, una modesta diminuzione delle precipitazioni annua-li, mentre la temperatura media annua appare in crescita. Con riferimento alle proie-zioni dei 13 modelli e alle precipitazioni annuali, invece, i risultati non sono concordan-ti; un riscaldamento dell'area di studio è invece constatabile univocamente dalle simu-lazioni esaminate. Infine, per verificare i segnali di cambiamento osservati, le proiezioni dei modelli climatici sono state confrontate con le tendenze basate sui dati storici. Si ottiene un accordo soddisfacente con riferimento alle precipitazioni; viene invece os-servata una sottostima sistematica dei valori di tendenza storicamente osservata rispet-to ai modelli, a medio e lungo termine, per i dati di temperatura
Analisi nel dominio del tempo della turbolenza nel campo di moto di un getto a simmetria assiale
No full textUse of numerical modeling to identify the transfer function and application to the geostatistical procedure in the solution of inverse problems in groundwater
No full textThe restoring of the pollutant release history makes use of transfer functions
(TFs) usually known by analytical formulation. In many cases the computation
of an analytical TF is not possible; this fact limits the application of the inverse procedures
to very simple conditions or it forces to drastic simplifications of complicated
problems. In this paper a new procedure, useful to compute the numerical transfer
functions in transport problems with no analytical solution, is outlined. This method,
analogous to the computation of the Instantaneous Unit Hydrograph (IUH) in surface
hydrology, makes use of mathematical modelling
The recovering of the pollutant release history in aquifer with non uniform transport process
No full textRecovering the pollutant release history in aquifers with non uniform flow field, Abstract H13D-1355
No full textThe great interest in environmental issues has led to an attention to the quality of groundwater.
Scientific efforts in groundwater flow studies have primarily focused on the flow and transport
behavior and on the identification of the corresponding parameters. Since ’90 increasing attention
has been paid to the problem of recovering the release history of a pollutant because the knowledge
of the pollution injection function gives information about the future pollution spread and allows a
better planning of remediation action (Liu and Ball, 1999, Snodgrass and Kitanidis, 1997, Skaggs
and Kabala, 1994, Butera and Tanda, 2003). Moreover, from a legal and regulatory point of view, it
is also important to determine the release time period and the highest values of concentration
released; in fact, an available release history can be a useful tool for sharing the costs of remediation
of a polluted area among the actors. Some approaches developed in the literature to the inverse
problem solution (geostatistical approach (Snodgrass and Kitanidis, 1997), Tikhonov regularization
method (Skaggs and Kabala, 1994)) require the computation of the function that describes the
effect, in time at a certain location of the aquifer, due to an impulsive release of pollutant at the
source. This function, named transfer or Kernel function can be analy1itically determined if the
problem has a simple geometry and regular boundary conditions. In many cases the characteristic of
the groundwater flow field do not allow for the analytical transfer function formulation; this is the
case, for instance, of non uniform in the mean flow due to complicated boundary conditions,
existence of pumping wells, high heterogeneity of the aquifer (Sudicky, 1986) etc.. With the
available procedures the technician has to reduce the real problem to a very simplified scheme to
which the analytical transfer function can be applied. As a consequence a rough approximation in
the results can be expected.
In this work, a numerical procedure useful to determine the transfer function in cases without
analytical solution is developed. It is based on the analogy with the techniques for identification of
the Instantaneous Unit Hydrograph used by the surface Hydrologists in determining the flood
response of a basin to a rain event
Recovering the pollutant release history in groundwater non uniform flow by means of an innovative procedure
No full textNew Applications of the Geostatistical Procedure in the Recovering of Pollutant Release History in Aquifers with Highly Heterogeneous Flow Field, Abstract H34A-0468
No full textThe interest in environmental issues has led great attention to the
quality of groundwater. Since '90 increasing attention has been paid to the
problem of recovering the release history of a pollutant because the knowledge of
the pollution injection function gives information about the future pollution
spread, allows a better planning of remediation actions and it can be a useful tool
for sharing the costs of remediation among the actors. The present work contains
the last results obtained through an inverse procedure (Snodgrass and Kitanidis,
1997) which allows the recovering of the pollutant release history from a few
concentration measurements; it is applied to very severe cases of non-uniform
flow conditions. The application of the inverse procedure is possible if one knows
the transfer function, which describes the transport process. This function can be
analytically determined if the problem has a simple geometry and regular
boundary conditions. The inverse procedure in hand, initially developed for a 1-D
homogeneous isotropic aquifer, has been extended by the writers (see Butera et
al., 2004) to multidimensional aquifers using the numerical modeling. In complex
cases, such as non-uniform flow field, reactive transport and unsaturated
aquifers, the transfer function can be numerically inferred using the methodology.
The applications showed in this meeting concern with very complicate flow
conditions that allow to evaluate the power of the methodology. Three cases are
presented: - The first analyzed case consists in a fully saturated aquifer with
highly heterogeneity conductivity field and a pumping well. - The second case
describes a fully saturated aquifer, highly heterogeneous, contaminated by a
reactive pollutant. - The last and most tricky case studies the diffusion of a
pollutant, due to the leakage from a tank, through an unsaturated aquifer. The
pollutant release history is satisfactory recovered in all of the studied cases
Artificial river ponds storing flood water as a resource for agriculture and groundwater recharge
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