HYDRAULICS
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- Versione italiana
- Academic year
- 2020/2021
- Teacher
- ALESSANDRO VALIANI
- Credits
- 6
- Didactic period
- Secondo Semestre
- SSD
- ICAR/01
Training objectives
- The module is the connection between the basic fluid mechanics and hydraulic engineering. It concerns one dimensional flow in pipes and channels. The module treats also some typical technical problems, even if with a basic approach, such the design and operating principles of networks pipes in steady and unsteady flow, and of open channels in uniform, steady and unsteady flow.
The main purpose of the module consists of applying fluid mechanics concepts (mass, momentum and energy balances), previously learnt in the fluid mechanics module, to hydraulics problems of technical interest, mainly one-dimensional flows and some classical problem in groundwater flows.
The main knowledge that should be acquired can be summarized as follows:
• Fundamental equations governing steady and unsteady motion in pressure pipes.
• Fundamental equations governing uniform, steady and un steady motion in artificial and natural open channel flows.
• Basic concepts of seepage flows.
• Basic concepts of laminar and turbulent boundary layers.
The main skills that should be acquired can be summarized as follows:
• To evaluate the flow resistances in both laminar and turbulent external and internal flows, with a specific attention to the latters.
• To design and verify simple systems of pressure pipes in steady and unsteady flow conditions.
• To design and verify open channels in uniform and steady flows.
• To properly set up unsteady flow problems in open channels. Prerequisites
- A deep attention to this aspect is required. Concerning the knowledge of the proper physical and mathematical tools, the rules concerning the Fluid mechanics module is addressed. Obviously, a productive attendance of the Hydraulics module requires the previous attendance of the Fluid mechanics module. The Hydraulics exam undergoing requires that the Fluid mechanics exam is previously passed.
Course programme
- 60 hours of lectures are planned. They consist of theoretical lectures, practical and numerical examples (52 h). Moreover, a specific support to practice exercises is provided for (8 h); these exercises are closely like those the students will find in the final written test. Numerical examples and practical aspects are deepened and explained.
The topics of the module are the following.
DIMENSIONAL ANALYSIS (4 h)
Buckingham Theorem. Non dimensional quantities in fluid mechanics.
STEADY FLOW IN CLOSED CONDUITS (8 h)
Cross section variations. Concentrated head losses. Pipes in series and in parallel. Syphons. Pipe networks. Distributed releases of discharge. Practical examples. Pumping and turbine plants.
UNSTEADY FLOWS IN CLOSED CONDUITS (10 h)
Continuity and momentum equations. Un steady uniform flow. Waterhammer problem. Wave celerity. Simplified equations. General solution. Initial and boundary conditions. Closing and opening valves. Overpressures. Chained Allievi equations. Graphical method. Methods of characteristics. Boundary conditions.
UNIFORM FLOW IN OPEN CHANNELS (5 h)
Specific energy and critical depth. Subcritical and supercritical flows. Critical depth. Resistance to flow. Stage-discharge curves. Compound channels.
STATIONARY FLOW IN OPEN CHANNELS (15 h)
Prismatic channels. Free surface profiles. Boundary conditions. Bresse solution. Non prismatic channels. Hydraulic jump and its position. Obstacles, abrupt changes, weirs.
UNSTEADY FLOW IN OPEN CHANNELS (3 h)
Small undulations propagation without friction. Method of characteristics. Boundary conditions.
GROUNDWATER FLOWS (3 h)
Fluid and grains properties. Darcy law. One dimensional seepage in phreatic and artesian aquifers. Phreatic and artesian wells.
PLANE IRROTATIONAL FLOWS
Velocity potential for irrotational flows. Vector potential for constant-volume flows. Streamfunction. Plane, constant-volume, irrotational flows. Simple flows and their superposition.
BOUNDARY LAYERS (4 h)
Laminar flow past a flat plate. Scale problems and dimensional analysis. Blasius solution. Turbulent boundary layer past a flat plate. Integral simplified momentum balance and relative solution. Boundary layer separation. Drag of the circular cylinder and of the sphere.
COMPLETE PERFORMANCE OF EXAMINATION EXERCISES (8 h) Didactic methods
- The lectures are organized as follows.
• Frontal lectures concerning the described topics;
• Practical examples, that are devoted to explain engineering applications of theoretical concepts;
• Support to carry out practical exercises (including numerical computations), that are extracted from written tests of previous academic years. Learning assessment procedures
- The main purpose of the final examination consists of verifying the proper achievement of the previously defined training objectives.
The exam is divided into two parts, a written test and the oral examination, in different dates.
• The written test (2.5 hours) consists of 2 exercises; each of them is evaluated as 1/2 of the total mark (15): 1) solving simple hydraulic networks; 2) solving steady flow in open channels of rectangular cross-section. A mark of 16/30 (at least) is required to sit the oral examination. The validity of the written text (if the mark is 18/30 at least) is twelve months. The validity of the written test, if the mark is less than 18/30, expires at the date of the following written text.
• The oral examination is mainly based on the topics not properly solved or not addressed in the written test. Open channel flows and water hammer problems are always faced. Moreover, a theoretical topic is also touched. The final mark is not the simple mean between written part and oral part (anyway is never less than this mean), but is a synthetic mark, expressed as a fraction of 30. If the candidate retreats during the oral examination, he must repeat the written test just if his mark on such test is less than 18/30. Reference texts
- Reference text: Lecture notes.
• MARCHI E., RUBATTA A., Meccanica dei fluidi. Principi ed applicazioni idrauliche. UTET, 1981.
• MOSSA M., PETRILLO A. F., Idraulica, CEA, Milano, 2013.
• MONTEFUSCO L., Lezioni di Idraulica. Pitagora Editrice, Bologna, 2005.
• CITRINI D., NOSEDA G., Idraulica. CEA, 1987.
• GHETTI A., Idraulica, Ed. Cortina, Padova, Ultima ediz. .
• LIGGET J.A., CAUGHEY D. A., FluidMechanics. An Interactive Text. ASCE Press, Reston, VA, 1998.
• WHITE F. M., Fluid Mechanics, Mc Graw Hill Intern. Student Ed., 1979.
• CENGEL Y.A., CIMBALA J. M., Meccanica dei fluidi, IV edizione, McGraw-Hill Education, Milano, 2020 (edizione italiana a cura di G. Cozzo e C. Santoro).
