Papers by Marco Placidi
Un documento ritrovato chiarisce svariati interrogativi
A triple slotted aerofoil following the Handley Page 44F design was tested at City University Lon... more A triple slotted aerofoil following the Handley Page 44F design was tested at City University London T-2 wind tunnel. The model allowed the study of a fixed triple slotted wing as well as investigation of the effects of isolated slots at different locations along the chord. PIV measurements were performed within the chord Reynolds number range in between approximately 200,000-400,000. The model was tested at an angle of attack of 22o. Measurements of mean streamwise velocity, velocity fluctuations and shear stress were analysed. The study shows how an isolated slot is more favourable when it is placed closest to the leading edge, although slow moving fluid regions can still be found close to the trailing edge. Fully attached flow was only achievable by using all three slots. In addition, the fully slotted profile is shown to generate channel exit velocities in the order of 1.4U∞, which highly energise the boundary layer on the suction side.
Der Degirmendere Aquadukt von Ephesos, 2019
8th AIAA Flow Control Conference, 2016
An experimental investigation on the influence of the spatial frequency content of roughness dist... more An experimental investigation on the influence of the spatial frequency content of roughness distributions on the development of crossflow instabilities has been carried out. From previous research it is known that micro roughness elements can have a large influence on the crossflow development. When the spanwise spacing is chosen such that it is the most unstable wavelength (following linear stability analysis), stationary crossflow waves are amplified. While in earlier studies the focus was on the height or spanwise spacing of roughness elements, in the present study it is chosen to vary the shape of the elements. Through the modification of the shape the forcing at the critical wavelength is increased, while the forcing at the harmonics of the critical wavelength is damped. Experiments were carried in the low turbulence wind tunnel at City University London (Tu=0.006%) on a swept flat plate in combination with displacement bodies to create a sufficiently strong favourable pressure gradient. Hot wire measurements across the plate tracked the development of stationary and travelling crossflow waves. Initially, stronger crossflow waves were found for the elements with stronger forcing, while further downstream the effect of forcing diminished. Spatial frequency spectra showed that the stronger forcing at the critical wavelength (via the roughness shape) dominates the response of the flow while low forcing at the harmonics has no notable effect. Additionally, high resolution streamwise hot wire scans showed that the onset of secondary instability is not significantly influenced by the spatial frequency content of the roughness distribution.
8th AIAA Flow Control Conference, 2016
This is the published version of the paper.
Springer Proceedings in Physics, 2016
The effects of sparsely distributed roughness elements on the structure of a turbulent boundary l... more The effects of sparsely distributed roughness elements on the structure of a turbulent boundary layer are examined by performing a series of Particle Image Velocimetry (PIV) experiments in a wind tunnel. From the literature, the best way to characterise a rough wall, especially one where the density of roughness elements is sparse, is unclear. In this study, rough surfaces consisting of sparsely and uniformly distributed LEGO^ blocks are used. Five different patterns are adopted in order to examine the effects of frontal solidity (λf, frontal area of the roughness elements per unit wall-parallel area), plan solidity (λp, plan area of roughness elements per unit wall-parallel area) and the geometry of the roughness element (square and cylindrical elements), on the turbulence structure. The Karman number, Reτ, has been matched, at the value of approximately 2300, in order to compare across the different cases. In the talk, we will present detailed analysis of mean and rms velocity pro...
This paper, a product of an intensive eight-week Lloyd’s Register Educational Trust (LRET) Colleg... more This paper, a product of an intensive eight-week Lloyd’s Register Educational Trust (LRET) Collegium held during July – September 2012 in Southampton, UK, presents an innovative engineering system concept design for manganese nodule recovery. Issues associated with environmental impacts, such as insufficient or lack of transparent impact studies of any potential full-scale seabed mining, are identified as the key obstacles which could lead to public protest, thus prevent the mining project from taking place. Hence, the proposed system introduces an environmentally friendly solution with the innovative concept of a black box, which performs in-situ nodule-sediment separation and waste discharge, and allows recirculation of waste water. The use of a modularised mining system with small, active hydraulic, crawler-type collectors is proposed to minimise environmental footprint and increase system redundancy. This yields a comparable estimated sediment-to-dry nodule ratio with previous s...
... La Strada Carrabile, dopo un primo tratto sotterraneo, proseguendo verso Sud diventa a cielo ... more ... La Strada Carrabile, dopo un primo tratto sotterraneo, proseguendo verso Sud diventa a cielo aperto per poi tornare ad essere di ... Placidi - Vittoria Fresi ● Tivoli, Villa Adriana, Strada sotterranea cd Strada Carrabile, Campagna di studio 2007-2008, breve sintesi dei risultati ...
A forgotten map of the Emissary of
lake Nemi, drafted before the 1928 works. A major
difficulty i... more A forgotten map of the Emissary of
lake Nemi, drafted before the 1928 works. A major
difficulty in the study of the ancient emissary of
lake Nemi is due to the fact that in 1928 the canal
underwent extensive rearrangements under the
direction of engineer Guido Ucelli, in order to permit
the drainage of the lake for the retrieval of ‘Caligula’s
ships’. In the absence of adequate documentation on
the emissary before such works, useful information can
be obtained from a map that was drafted in 1926 by
an ad hoc ministerial commission and that has hitherto
escaped the attention of scholars. Such a map is not
exempt from glaring mistakes and approximations,
but it provides valuable details on the dimensions of
the ancient artefact, its practicability, the existence of
shafts, the chronology of some tunnel fillings.
The Emissarium of Lake Nemi - The two emissaria of Lake Albanus and Lake Nemi in the Castelli
Rom... more The Emissarium of Lake Nemi - The two emissaria of Lake Albanus and Lake Nemi in the Castelli
Romani are engineering works that have aroused interest among scholars because the few bibliographical sources
available never have allowed a complete and satisfactory understanding. In particular the emissarium of Lake
Nemi suffers from the lack of historical and literary sources, if one leaves out the meagre documentation put
together on the occasion of its reuse for the recovery of the ships of Caligula by Ucelli in 1928 – 1932. In recent
decades the emissarium of Lake Nemi has been studied first by Cappa and then more thoroughly by Castellani
whose studies ended in 2006, the year of his death. Since 2008 the Centro Ricerche Speleo Archeologiche (CRSA)
is undertaking a study campaign of the emissarium of Lake Nemi with the aim to integrate the research of
Castellani and draw a conclusion. In the article a few interpretations concerning the excavation of the two
bypasses are being proposed. The first bypass was most likely created after part of the tunnel had collapsed and
the second one to solve the problem of water infiltration and dispersion into the ground. As to the inlet (incile),
i.e. the monumental entrance , the presence of some vertical slots suggests that these could have served to insert
panels to block the flow of water in order to allow the launch of the Caligula’s ships.
The Great Underground Road, the “Strada Carrabile” of Hadrian’s Villa. This article presents the ... more The Great Underground Road, the “Strada Carrabile” of Hadrian’s Villa. This article presents the main
results of a study campaign (2007-2009) focusing on the underground road system of Hadrian’s Villa (Tivoli), also
known as “Strada Carrabile” or “Driveway” that led to the so-called Great Trapezium. The extensive underground
network is an ingenious system connecting the different quarters of the villa and is composed of underground
passages for people on foot and in carts. The underground infrastructure hid the traffic of the slaves and helped
to respect the emperor’s demands of order and tranquillity. Towards the far north of the Terrace of Tempe there
is the entrance to an originally artificial cavity that has never been documented. On first inspection it has been
identified as a hypothetical underground road far bigger than the passages already explored. The height cannot
be determined yet, since the debris fills it almost to the vault. We have been able to explore only the first 60
metres from the entrance. The tunnel first runs north-east for about 50 metres and then turns towards the south.
Indagine speleo archeologica nel comune di Gallicano nel lazio su l'acquedotto Marcio e Anio vetu... more Indagine speleo archeologica nel comune di Gallicano nel lazio su l'acquedotto Marcio e Anio vetus. Lescoperte consistono nello studio sistematico della 'galleria della Bulica",di un attraversamento dell'acquedotto sotto il letto del torrente e della realizzazione di una diga per superare un tratto fatiscentedell'acquedotto a ponte Pischero.
Teaching Documents by Marco Placidi
Il CRSA – Centro Ricerche Speleo archeologiche
organizza corsi introduttivi alla speleo-archeolog... more Il CRSA – Centro Ricerche Speleo archeologiche
organizza corsi introduttivi alla speleo-archeologia
rivolti ai neoiti che intendano approfondire le
tecniche di esplorazione, studio e ricerca di sotterranei
di interesse archeologico e di chiara origine
antropica.
Books by Marco Placidi
Indagini sui sistemi ipogei del colle Palatino, 2010
Indagini degli ipogei presenti sul Palatino, in occasione degli interventi per la tutela e la fru... more Indagini degli ipogei presenti sul Palatino, in occasione degli interventi per la tutela e la fruizione del patrimonio archeologico - Secondo rapporto 2009-2010
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Papers by Marco Placidi
lake Nemi, drafted before the 1928 works. A major
difficulty in the study of the ancient emissary of
lake Nemi is due to the fact that in 1928 the canal
underwent extensive rearrangements under the
direction of engineer Guido Ucelli, in order to permit
the drainage of the lake for the retrieval of ‘Caligula’s
ships’. In the absence of adequate documentation on
the emissary before such works, useful information can
be obtained from a map that was drafted in 1926 by
an ad hoc ministerial commission and that has hitherto
escaped the attention of scholars. Such a map is not
exempt from glaring mistakes and approximations,
but it provides valuable details on the dimensions of
the ancient artefact, its practicability, the existence of
shafts, the chronology of some tunnel fillings.
Romani are engineering works that have aroused interest among scholars because the few bibliographical sources
available never have allowed a complete and satisfactory understanding. In particular the emissarium of Lake
Nemi suffers from the lack of historical and literary sources, if one leaves out the meagre documentation put
together on the occasion of its reuse for the recovery of the ships of Caligula by Ucelli in 1928 – 1932. In recent
decades the emissarium of Lake Nemi has been studied first by Cappa and then more thoroughly by Castellani
whose studies ended in 2006, the year of his death. Since 2008 the Centro Ricerche Speleo Archeologiche (CRSA)
is undertaking a study campaign of the emissarium of Lake Nemi with the aim to integrate the research of
Castellani and draw a conclusion. In the article a few interpretations concerning the excavation of the two
bypasses are being proposed. The first bypass was most likely created after part of the tunnel had collapsed and
the second one to solve the problem of water infiltration and dispersion into the ground. As to the inlet (incile),
i.e. the monumental entrance , the presence of some vertical slots suggests that these could have served to insert
panels to block the flow of water in order to allow the launch of the Caligula’s ships.
results of a study campaign (2007-2009) focusing on the underground road system of Hadrian’s Villa (Tivoli), also
known as “Strada Carrabile” or “Driveway” that led to the so-called Great Trapezium. The extensive underground
network is an ingenious system connecting the different quarters of the villa and is composed of underground
passages for people on foot and in carts. The underground infrastructure hid the traffic of the slaves and helped
to respect the emperor’s demands of order and tranquillity. Towards the far north of the Terrace of Tempe there
is the entrance to an originally artificial cavity that has never been documented. On first inspection it has been
identified as a hypothetical underground road far bigger than the passages already explored. The height cannot
be determined yet, since the debris fills it almost to the vault. We have been able to explore only the first 60
metres from the entrance. The tunnel first runs north-east for about 50 metres and then turns towards the south.
Teaching Documents by Marco Placidi
organizza corsi introduttivi alla speleo-archeologia
rivolti ai neoiti che intendano approfondire le
tecniche di esplorazione, studio e ricerca di sotterranei
di interesse archeologico e di chiara origine
antropica.
Books by Marco Placidi
lake Nemi, drafted before the 1928 works. A major
difficulty in the study of the ancient emissary of
lake Nemi is due to the fact that in 1928 the canal
underwent extensive rearrangements under the
direction of engineer Guido Ucelli, in order to permit
the drainage of the lake for the retrieval of ‘Caligula’s
ships’. In the absence of adequate documentation on
the emissary before such works, useful information can
be obtained from a map that was drafted in 1926 by
an ad hoc ministerial commission and that has hitherto
escaped the attention of scholars. Such a map is not
exempt from glaring mistakes and approximations,
but it provides valuable details on the dimensions of
the ancient artefact, its practicability, the existence of
shafts, the chronology of some tunnel fillings.
Romani are engineering works that have aroused interest among scholars because the few bibliographical sources
available never have allowed a complete and satisfactory understanding. In particular the emissarium of Lake
Nemi suffers from the lack of historical and literary sources, if one leaves out the meagre documentation put
together on the occasion of its reuse for the recovery of the ships of Caligula by Ucelli in 1928 – 1932. In recent
decades the emissarium of Lake Nemi has been studied first by Cappa and then more thoroughly by Castellani
whose studies ended in 2006, the year of his death. Since 2008 the Centro Ricerche Speleo Archeologiche (CRSA)
is undertaking a study campaign of the emissarium of Lake Nemi with the aim to integrate the research of
Castellani and draw a conclusion. In the article a few interpretations concerning the excavation of the two
bypasses are being proposed. The first bypass was most likely created after part of the tunnel had collapsed and
the second one to solve the problem of water infiltration and dispersion into the ground. As to the inlet (incile),
i.e. the monumental entrance , the presence of some vertical slots suggests that these could have served to insert
panels to block the flow of water in order to allow the launch of the Caligula’s ships.
results of a study campaign (2007-2009) focusing on the underground road system of Hadrian’s Villa (Tivoli), also
known as “Strada Carrabile” or “Driveway” that led to the so-called Great Trapezium. The extensive underground
network is an ingenious system connecting the different quarters of the villa and is composed of underground
passages for people on foot and in carts. The underground infrastructure hid the traffic of the slaves and helped
to respect the emperor’s demands of order and tranquillity. Towards the far north of the Terrace of Tempe there
is the entrance to an originally artificial cavity that has never been documented. On first inspection it has been
identified as a hypothetical underground road far bigger than the passages already explored. The height cannot
be determined yet, since the debris fills it almost to the vault. We have been able to explore only the first 60
metres from the entrance. The tunnel first runs north-east for about 50 metres and then turns towards the south.
organizza corsi introduttivi alla speleo-archeologia
rivolti ai neoiti che intendano approfondire le
tecniche di esplorazione, studio e ricerca di sotterranei
di interesse archeologico e di chiara origine
antropica.